Quant Formula Book
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Apr 10, 2023
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About This Presentation
This formula book is based on the Quant section for CAT Exam Preparation. You can start your preparation by reading this E-book.
Slide Content
Quantitative
aptitude
Formula book
curated & updated by cat
mentors for all management
Exams
aptitude
Formula book
curated & updated by cat
mentors for all management
Exams
Chapter – 1 Calculation Tricks ______________ 01
A. List of important fractions 01
B. Important Tables, squares and cubes 02
Chapter – 2 Conversion of Units _____________ 03
Chapter – 3 Number System _______________ 04
A. Types of No. 04
B. Operation on odd and even numbers 06
C. Test of Divisibility 06
D. Properties of numbers 07
E. LCM & HCF 08
F. Fractions 08
G. Indices 09
H. Remainder Theory 10
Chapter – 4 Average _______________ 11
Chapter – 5 Basic Algebra _______________ 11
A. Algebraic Formulae 11
B. Linear Equations 11
C. Quadratic Equations 12
D. Inequalities 12
E. Arithmetic and Geometric Progression 13
F. Special Equations 14
G. Cauchy’s functional equations 14
Chapter – 6 Percentage and Profit & Loss ______________ 15
A. Percentage 15
B. Simple interest and Compound interest 16
C. Profit & Loss 17
CONTENTS
A. List of important fractions 01
B. Important Tables, squares and cubes 02
Chapter – 2 Conversion of Units _____________ 03
Chapter – 3 Number System _______________ 04
A. Types of No. 04
B. Operation on odd and even numbers 06
C. Test of Divisibility 06
D. Properties of numbers 07
E. LCM & HCF 08
F. Fractions 08
G. Indices 09
H. Remainder Theory 10
Chapter – 4 Average _______________ 11
Chapter – 5 Basic Algebra _______________ 11
A. Algebraic Formulae 11
B. Linear Equations 11
C. Quadratic Equations 12
D. Inequalities 12
E. Arithmetic and Geometric Progression 13
F. Special Equations 14
G. Cauchy’s functional equations 14
Chapter – 6 Percentage and Profit & Loss ______________ 15
A. Percentage 15
B. Simple interest and Compound interest 16
C. Profit & Loss 17
CONTENTS
Chapter – 7 Ratio, Mixture and Partnership _______________ 18
A. Ratio and Proportion 18
B. Alligation and Mixture 19
C. Partnership 19
Chapter – 8 Time and Work _______________ 20
Chapter – 9 Time Speed & Distance _____________ 20
A. Basics of Time Speed Distance 20
B. Boats and Steams 21
C. Races 21
Chapter – 10 Geometry & Mensuration _______________ 22
A. Rectangular solids and cylinders 22
B. Lines and Angles 23
C. Triangles 26
D. Circles 31
E. Quadrilateral & Polygons 35
A. Clocks 43
B. Calendars 43
Chapter – 17 Mean and Basic Statistics _______________ 44
Chapter – 11 Coordinate Geometry _______________ 36
Chapter – 12 Set Theory ________________ 37
Chapter – 13 Logarithms ________________ 38
Chapter – 14 Permutation & Combination ________________ 39
Chapter – 15 Probability __________________ 41
Chapter – 16 Clocks and Calendars ___________________ 43
Chapter – 18 Trigonometry __________________ 45
A. Ratio and Proportion 18
B. Alligation and Mixture 19
C. Partnership 19
Chapter – 8 Time and Work _______________ 20
Chapter – 9 Time Speed & Distance _____________ 20
A. Basics of Time Speed Distance 20
B. Boats and Steams 21
C. Races 21
Chapter – 10 Geometry & Mensuration _______________ 22
A. Rectangular solids and cylinders 22
B. Lines and Angles 23
C. Triangles 26
D. Circles 31
E. Quadrilateral & Polygons 35
A. Clocks 43
B. Calendars 43
Chapter – 17 Mean and Basic Statistics _______________ 44
Chapter – 11 Coordinate Geometry _______________ 36
Chapter – 12 Set Theory ________________ 37
Chapter – 13 Logarithms ________________ 38
Chapter – 14 Permutation & Combination ________________ 39
Chapter – 15 Probability __________________ 41
Chapter – 16 Clocks and Calendars ___________________ 43
Chapter – 18 Trigonometry __________________ 45
1. Calculation Tricks
A. List of important fractions
You get many questions in the exams based on Percentage, Profit, Interest etc. in
which you have to calculate, say 87.5% of 800, 58.33 % of 2400 etc. Calculating
these values with the help of traditional methods is time-consuming.
If you apply the fraction approach, you can crack these easily i.e., if you know that
87.5% is just 7/8th of the number and 58.33 % is 7/12th of the number, then it
becomes easy to calculate.
Given below are the important fractions, which you should remember:
% age Fraction % age Fraction
50 % 1
2 5
55 %
9 5
9 1
33 %
3
1
3 7
77 %
9 7
9 2
66 %
3
2
3 8
88 %
9 8
9
25 % 1
4
75 % 3
4 1
9%
11 1
11
20 % 1
5 2
18 %
11 2
11
40 % 2
5 3
27 %
11 3
11
60 % 3
5 4
36 %
11 4
11
80 % 4
5 5
45 %
11 5
11 2
16 %
3
1
6 7
63 %
11 7
11 1
83 %
3
5
6 8
72 %
11 8
11 2
14 %
7
1
7 9
81 %
11 9
11 1
12 %
2
1
8 1
37 %
2
3
8 1
8%
3 1
12 1
62 %
2
5
8 2
41 %
3 5
12 1
87 %
2
7
8 1
58 %
3 7
12 1
11 %
9
1
9 2
6%
3 1
15 2
22 %
9
2
9 1
6%
4 1
16 1 Ekoching
Your door to future
A. List of important fractions
You get many questions in the exams based on Percentage, Profit, Interest etc. in
which you have to calculate, say 87.5% of 800, 58.33 % of 2400 etc. Calculating
these values with the help of traditional methods is time-consuming.
If you apply the fraction approach, you can crack these easily i.e., if you know that
87.5% is just 7/8th of the number and 58.33 % is 7/12th of the number, then it
becomes easy to calculate.
Given below are the important fractions, which you should remember:
% age Fraction % age Fraction
50 % 1
2 5
55 %
9 5
9 1
33 %
3
1
3 7
77 %
9 7
9 2
66 %
3
2
3 8
88 %
9 8
9
25 % 1
4
75 % 3
4 1
9%
11 1
11
20 % 1
5 2
18 %
11 2
11
40 % 2
5 3
27 %
11 3
11
60 % 3
5 4
36 %
11 4
11
80 % 4
5 5
45 %
11 5
11 2
16 %
3
1
6 7
63 %
11 7
11 1
83 %
3
5
6 8
72 %
11 8
11 2
14 %
7
1
7 9
81 %
11 9
11 1
12 %
2
1
8 1
37 %
2
3
8 1
8%
3 1
12 1
62 %
2
5
8 2
41 %
3 5
12 1
87 %
2
7
8 1
58 %
3 7
12 1
11 %
9
1
9 2
6%
3 1
15 2
22 %
9
2
9 1
6%
4 1
16 1 Ekoching
Your door to future
Anything doubles to increase by 100 % and becomes 200%.
Anything trebles to increase by 200% and becomes 300%.
B. Important Tables, Squares and Cubes
In order to be good at mathematics, you have to be good at calculations. For
improving calculations, you have to be good at numbers and tables. You should
start with tables and make it the most important part of your preparation
Tables: Learn all these tables by heart and see how you improve your calculation
speed.
Table 12 13 14 15 16 17 18 19
T 1 12 13 14 15 16 17 18 19
T 2 24 26 28 30 32 34 36 38
T 3 36 39 42 45 48 51 54 57
T 4 48 52 56 60 64 68 72 76
T 5 60 65 70 75 80 85 90 95
T 6 72 78 84 90 96 102 108 114
T 7 84 91 98 105 112 119 126 133
T 8 96 104 112 120 128 136 144 152
T 9 108 117 126 135 144 153 162 171
T 10 120 130 140 150 160 170 180 190
Squarest : Learn these squares by heart.
Z Z
2
Z Z
2
Z Z
2
1 1 13 169 25 625
2 4 14 196 26 676
3 9 15 225 27 729
4 16 16 256 28 784
5 25 17 289 29 841
6 36 18 324 30 900
7 49 19 361 31 961
8 64 20 400 32 1024
9 81 21 441 33 1089
10 100 22 484 34 1156
11 121 23 529 35 1225
12 144 24 576
Cubes : Leam these cubes by heart.
Y Y
3
Y Y
3
1 1 12 1728
2 8 13 2197
3 27 14 2744
4 64 15 3375 4
44 %
9
4
9 5 % 1
20 2 Ekoching
Your door to future
Anything trebles to increase by 200% and becomes 300%.
B. Important Tables, Squares and Cubes
In order to be good at mathematics, you have to be good at calculations. For
improving calculations, you have to be good at numbers and tables. You should
start with tables and make it the most important part of your preparation
Tables: Learn all these tables by heart and see how you improve your calculation
speed.
Table 12 13 14 15 16 17 18 19
T 1 12 13 14 15 16 17 18 19
T 2 24 26 28 30 32 34 36 38
T 3 36 39 42 45 48 51 54 57
T 4 48 52 56 60 64 68 72 76
T 5 60 65 70 75 80 85 90 95
T 6 72 78 84 90 96 102 108 114
T 7 84 91 98 105 112 119 126 133
T 8 96 104 112 120 128 136 144 152
T 9 108 117 126 135 144 153 162 171
T 10 120 130 140 150 160 170 180 190
Squarest : Learn these squares by heart.
Z Z
2
Z Z
2
Z Z
2
1 1 13 169 25 625
2 4 14 196 26 676
3 9 15 225 27 729
4 16 16 256 28 784
5 25 17 289 29 841
6 36 18 324 30 900
7 49 19 361 31 961
8 64 20 400 32 1024
9 81 21 441 33 1089
10 100 22 484 34 1156
11 121 23 529 35 1225
12 144 24 576
Cubes : Leam these cubes by heart.
Y Y
3
Y Y
3
1 1 12 1728
2 8 13 2197
3 27 14 2744
4 64 15 3375 4
44 %
9
4
9 5 % 1
20 2 Ekoching
Your door to future
5 125 6 4096
6 216 17 4913
7 343 18 5832
8 512 19 6859
9 729 20 8000
10 1000 21 9261
11 1331 22 10648
2. Conversions of Units
Number of zeroes in
1 Lakh = 5 100,000
1 Crore = 7= 10,000,000
1 million 61,000,000
1 Billion = 9=1,000,000,000
Linear Measures (Metric)
1. 10 millimeters (mm) = 1 centimeter (cm)
2. 10 centimeters = 1 decimeter (dm)
3. 10 decimeters = 1 meter (m or M)
4. 10 meters = 1 Decameter (Dm)
6. 10 Hectometers = 1 Kilometer (Km)= 1000 m = 100,000 cm
5. 10 Decameter= 1 Hectometer (Hm)
British
1. 12 inches (in) 1 foot (ft) 3. 220 yards 1 furlong Relationship
2. 3 feet = 1 yard (yd)
4. 8 furlongs 1 mile = 1760 yards = 5280 ft
Relationship
1.1 inch = 2.54 cm
3.1 mile 1600 m
5. 1 mile 1.6 km = 1600 meters..
2. 1 Km = 5 furlongs
4. 1 meter = 1.1 yds = 3.39 ft
Area Measures
Metric
1. 1 Hectare = 1 sq. Hm = 10,000 Sq. m
British
1. 1 acre = 4840 sq. yds = 40,000 sq ft.
2. 1 are 120 sq. yds
3. 40 ares 1 acre
4. 1 cent = 440 sq ft.
Relationship
1. 1 Hectare = 2.5 acres
Volume Measures 3 Ekoching
Your door to future
6 216 17 4913
7 343 18 5832
8 512 19 6859
9 729 20 8000
10 1000 21 9261
11 1331 22 10648
2. Conversions of Units
Number of zeroes in
1 Lakh = 5 100,000
1 Crore = 7= 10,000,000
1 million 61,000,000
1 Billion = 9=1,000,000,000
Linear Measures (Metric)
1. 10 millimeters (mm) = 1 centimeter (cm)
2. 10 centimeters = 1 decimeter (dm)
3. 10 decimeters = 1 meter (m or M)
4. 10 meters = 1 Decameter (Dm)
6. 10 Hectometers = 1 Kilometer (Km)= 1000 m = 100,000 cm
5. 10 Decameter= 1 Hectometer (Hm)
British
1. 12 inches (in) 1 foot (ft) 3. 220 yards 1 furlong Relationship
2. 3 feet = 1 yard (yd)
4. 8 furlongs 1 mile = 1760 yards = 5280 ft
Relationship
1.1 inch = 2.54 cm
3.1 mile 1600 m
5. 1 mile 1.6 km = 1600 meters..
2. 1 Km = 5 furlongs
4. 1 meter = 1.1 yds = 3.39 ft
Area Measures
Metric
1. 1 Hectare = 1 sq. Hm = 10,000 Sq. m
British
1. 1 acre = 4840 sq. yds = 40,000 sq ft.
2. 1 are 120 sq. yds
3. 40 ares 1 acre
4. 1 cent = 440 sq ft.
Relationship
1. 1 Hectare = 2.5 acres
Volume Measures 3 Ekoching
Your door to future
Metric
1. 1 cubic centimeter (cc) = 1 milliliter (ml).
2. 10 ml 1 centiliter (cl).
3. 10 cl 1 deciliter (dl).
4. 10 dl 1 liter (L or I)= 1000 ml = 1000 cc.
5. 1000 liter = 1 Kilo liter (KI).
British
1. 20 ounces (oz) = 1 pint
2. 8 pints = 1 gallon
Relationship
1. 1 gallon = 4.55 liters or 1 liter = 0.22 gallon.
Weight Measures
Metric
1. 10 milligrams (mg) = 1 centigram (cgm)
2. 10 centigrams = 1 decigram (dgm)
3. 10 decigrams = 1 gram (gm)
4. 10 grams = 1 Decagram (Dgm)
5. 10 Decagrams = 1 Hectogram (Hgm)
6. 10 Hectograms = 1 Kilogram (Kg) = 1000 gm
7. 100 Kg = 1 quintal
8. 10 quintals 1 Metric Ton= 1000 Kg
British
1. 12 ounce (oz) = 1 pound (lb)
2. 14 pounds = 1 quarter (gr)
3. 4 quarters = 1 hundred weight (cwt)
4. 4. 20 hundred weights = 1 ton
5. 5. 1 ton 2240 pounds
Speed Measures.
Metric
1 km = 1000 meters 1 hr = 3600 seconds
1 1000 5
1km/ hr m/sec
1 3600 18
British
1 mile = 1760 yards 1 yard = 3 feet
1 mile = 5280 feet 1 1760 22
1 mph yards/sec
1 3600 45
1 5280 22
1 mph ft /sec
1 3600 15
3. Number System
A. Types of Numbers
Following are different types of numbers which we generally use in our
calculations.
Natural Numbers: The numbers 1,2,3,4.... are called natural numbers or positive
integers. 4 Ekoching
Your door to future
1. 1 cubic centimeter (cc) = 1 milliliter (ml).
2. 10 ml 1 centiliter (cl).
3. 10 cl 1 deciliter (dl).
4. 10 dl 1 liter (L or I)= 1000 ml = 1000 cc.
5. 1000 liter = 1 Kilo liter (KI).
British
1. 20 ounces (oz) = 1 pint
2. 8 pints = 1 gallon
Relationship
1. 1 gallon = 4.55 liters or 1 liter = 0.22 gallon.
Weight Measures
Metric
1. 10 milligrams (mg) = 1 centigram (cgm)
2. 10 centigrams = 1 decigram (dgm)
3. 10 decigrams = 1 gram (gm)
4. 10 grams = 1 Decagram (Dgm)
5. 10 Decagrams = 1 Hectogram (Hgm)
6. 10 Hectograms = 1 Kilogram (Kg) = 1000 gm
7. 100 Kg = 1 quintal
8. 10 quintals 1 Metric Ton= 1000 Kg
British
1. 12 ounce (oz) = 1 pound (lb)
2. 14 pounds = 1 quarter (gr)
3. 4 quarters = 1 hundred weight (cwt)
4. 4. 20 hundred weights = 1 ton
5. 5. 1 ton 2240 pounds
Speed Measures.
Metric
1 km = 1000 meters 1 hr = 3600 seconds
1 1000 5
1km/ hr m/sec
1 3600 18
British
1 mile = 1760 yards 1 yard = 3 feet
1 mile = 5280 feet 1 1760 22
1 mph yards/sec
1 3600 45
1 5280 22
1 mph ft /sec
1 3600 15
3. Number System
A. Types of Numbers
Following are different types of numbers which we generally use in our
calculations.
Natural Numbers: The numbers 1,2,3,4.... are called natural numbers or positive
integers. 4 Ekoching
Your door to future
Whole Numbers: The numbers 0,1,2,3.... are called whole numbers. Whole
numbers include "0". Every Natural number is a whole number but the converse
is not true.
Integers: The numbers.... -3, -2, -1, 0, 1, 2, 3,.... are called integers. Every Whole
number is an integer but the converse is not true.
Negative Integers: The numbers -1, -2, -3, are called negative integers.
Rational Numbers: Any number which is a positive or negative integer or fraction,
or zero is called a rational number. A rational number is one which can be
expressed in the following format, a
,
b
where b 0 and a & b are positive or
negative integers. Every Integer is a rational number but the converse is not true.
Positive Fractions: The numbers 2 4 7
,,
358 …. are called positive fractions.
Negative Fractions: The numbers 6 7 12
, , ....
8 19 47
are called negative fractions.
Note: Between any two different rational numbers a & b there always exists a
rational number calculated by taking the average of a and b i.e. ab
2
Irrational Numbers: A non terminating non recurring decimal number is known as
an irrational number. These numbers cannot be expressed in the form of a proper
fraction a/b where b 0.
e.g. 2, 5, ,etc.
Even Numbers: The numbers which are divisible by 2 are called even numbers e.g.
-4, 0, 2, 16 etc.
Odd Numbers: The numbers which are not divisible by 2 are odd numbers e.g. -7,
-15, 5, 9 etc.
Prime Numbers: Those numbers, which are divisible only by themselves and 1, are
called prime numbers. In other words, a number, which has exactly two factors –
1 and itself, is called a prime number. e.g. 2, 3, 5, 7, etc.
2 is the only even prime number.
There are 25 prime numbers up to 100. These are 2, 3, 5, 7, 11, 13, 17, 19, 23, 29,
31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89 & 97. These should be learnt by
heart.
Composite Number: A number, which has more than two factors, is called a
composite number. e.g. 9, 10, 15, 16,……
A composite number can be expressed as the product of prime numbers in a
unique way. e.g. 100 = 2
2
x 5
2
1 is neither a composite number nor a prime number. 5 Ekoching
Your door to future
numbers include "0". Every Natural number is a whole number but the converse
is not true.
Integers: The numbers.... -3, -2, -1, 0, 1, 2, 3,.... are called integers. Every Whole
number is an integer but the converse is not true.
Negative Integers: The numbers -1, -2, -3, are called negative integers.
Rational Numbers: Any number which is a positive or negative integer or fraction,
or zero is called a rational number. A rational number is one which can be
expressed in the following format, a
,
b
where b 0 and a & b are positive or
negative integers. Every Integer is a rational number but the converse is not true.
Positive Fractions: The numbers 2 4 7
,,
358 …. are called positive fractions.
Negative Fractions: The numbers 6 7 12
, , ....
8 19 47
are called negative fractions.
Note: Between any two different rational numbers a & b there always exists a
rational number calculated by taking the average of a and b i.e. ab
2
Irrational Numbers: A non terminating non recurring decimal number is known as
an irrational number. These numbers cannot be expressed in the form of a proper
fraction a/b where b 0.
e.g. 2, 5, ,etc.
Even Numbers: The numbers which are divisible by 2 are called even numbers e.g.
-4, 0, 2, 16 etc.
Odd Numbers: The numbers which are not divisible by 2 are odd numbers e.g. -7,
-15, 5, 9 etc.
Prime Numbers: Those numbers, which are divisible only by themselves and 1, are
called prime numbers. In other words, a number, which has exactly two factors –
1 and itself, is called a prime number. e.g. 2, 3, 5, 7, etc.
2 is the only even prime number.
There are 25 prime numbers up to 100. These are 2, 3, 5, 7, 11, 13, 17, 19, 23, 29,
31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89 & 97. These should be learnt by
heart.
Composite Number: A number, which has more than two factors, is called a
composite number. e.g. 9, 10, 15, 16,……
A composite number can be expressed as the product of prime numbers in a
unique way. e.g. 100 = 2
2
x 5
2
1 is neither a composite number nor a prime number. 5 Ekoching
Your door to future
Real Numbers: The above sets of natural numbers, integers, whole numbers,
rational numbers and irrational numbers constitute the set of real numbers. Every
real number can be represented by a point on a number line.
Perfect Numbers: If the sum of all the factors of a number excluding the number
itself happens to be equal to the number, then the number is called as perfect
number. 6 is the first perfect number. The factors of 6 are 1, 2, 3 & 6. Leaving 6 the
sum of other factors of 6 are equal to 6. The next three perfect numbers after 6 are
28, 496 and 8128.
B. Operations on Odd & Even Numbers
(i) Addition or subtraction of any two odd numbers will always result in an
even number or zero. E.g. 1 +3=4; 5-3=2.
(ii) Addition or subtraction of any two even numbers will always result in an
even number or zero. E.g. 2+4= 6; 12-4=8.
(iii) Addition or subtraction of an even number from an odd number will result
in an odd number. E.g. 2+4=7;5-2=3.
(iv) Addition or subtraction of an even number from an odd number will result
in an odd number. E.g. 3 + 4 =7 ; 5 – 2 =3.
(v) Multiplication of two odd numbers will result in an odd number. E.g. 3 x3
= 9.
(vi) Multiplication of two even numbers will result in an even number. E.g. 2 x
4 = 8.
(vii) Multiplication of an odd number by an even number or vice versa will
result in an even number. E.g. 3x2=6.
(viii) An odd number raised to an odd or an even power is always odd.
(ix) An even number raised to an odd or an even power is always even.
(x) The standard form of writing a number is m x 10" where m lies between 1
and 10 and n is an integer. e.g. 0.89713 8.9713/10
1
8.9713 x 10
-
¹.
(xi) If n is odd. n(n
2
-1) is divisible by 24. e.g. take n = 5(5
2
-1) = 120, which is
divisible by 24.
(xii) If n is odd prime number except 3, then n²-1 is divisible by 24.
(xiii) If n is odd. 2" + 1 is divisible by 3.
(xiv) If n is even. 2" - 1 is divisible by 3.
(xv) If n is odd, 22+ 1 is divisible by 5.
(xvi) If n is even, 22n-1 is divisible by 5.
(xvii) If n is odd, 52n + 1 is divisible by 13.
(xviii) If n is even, 52n-1 is divisible by 13
C. Tests of Divisibility
Divisibility rules are very helpful while doing calculations. Following are some
important divisibility rules which you should learn from heart.
(i) By 2 - A number is divisible by 2 when its units place is 0 or divisible by 2. e.g.
120, 138.
(ii) By 3 - A number is divisible by 3 when the sum of the digits of the number is
divisible by 3. e.g. 15834 is divisible by 3 as the sum of its digits is 21 which is 6 Ekoching
Your door to future
rational numbers and irrational numbers constitute the set of real numbers. Every
real number can be represented by a point on a number line.
Perfect Numbers: If the sum of all the factors of a number excluding the number
itself happens to be equal to the number, then the number is called as perfect
number. 6 is the first perfect number. The factors of 6 are 1, 2, 3 & 6. Leaving 6 the
sum of other factors of 6 are equal to 6. The next three perfect numbers after 6 are
28, 496 and 8128.
B. Operations on Odd & Even Numbers
(i) Addition or subtraction of any two odd numbers will always result in an
even number or zero. E.g. 1 +3=4; 5-3=2.
(ii) Addition or subtraction of any two even numbers will always result in an
even number or zero. E.g. 2+4= 6; 12-4=8.
(iii) Addition or subtraction of an even number from an odd number will result
in an odd number. E.g. 2+4=7;5-2=3.
(iv) Addition or subtraction of an even number from an odd number will result
in an odd number. E.g. 3 + 4 =7 ; 5 – 2 =3.
(v) Multiplication of two odd numbers will result in an odd number. E.g. 3 x3
= 9.
(vi) Multiplication of two even numbers will result in an even number. E.g. 2 x
4 = 8.
(vii) Multiplication of an odd number by an even number or vice versa will
result in an even number. E.g. 3x2=6.
(viii) An odd number raised to an odd or an even power is always odd.
(ix) An even number raised to an odd or an even power is always even.
(x) The standard form of writing a number is m x 10" where m lies between 1
and 10 and n is an integer. e.g. 0.89713 8.9713/10
1
8.9713 x 10
-
¹.
(xi) If n is odd. n(n
2
-1) is divisible by 24. e.g. take n = 5(5
2
-1) = 120, which is
divisible by 24.
(xii) If n is odd prime number except 3, then n²-1 is divisible by 24.
(xiii) If n is odd. 2" + 1 is divisible by 3.
(xiv) If n is even. 2" - 1 is divisible by 3.
(xv) If n is odd, 22+ 1 is divisible by 5.
(xvi) If n is even, 22n-1 is divisible by 5.
(xvii) If n is odd, 52n + 1 is divisible by 13.
(xviii) If n is even, 52n-1 is divisible by 13
C. Tests of Divisibility
Divisibility rules are very helpful while doing calculations. Following are some
important divisibility rules which you should learn from heart.
(i) By 2 - A number is divisible by 2 when its units place is 0 or divisible by 2. e.g.
120, 138.
(ii) By 3 - A number is divisible by 3 when the sum of the digits of the number is
divisible by 3. e.g. 15834 is divisible by 3 as the sum of its digits is 21 which is 6 Ekoching
Your door to future
divisible by 3. Note that if n is odd, then 2" + 1 is divisible by 3 and if n is even,
then 2" - 1 is divisible by 3.
(iii) By 4 - A number is divisible by 4 when the last two digits of the number are
Os or are divisible by 4. As 100 is divisible by 4, it is sufficient if the divisibility test
is restricted to the last two digits. e.g. 145896, 128, 18400
(iv) By 5- A number is divisible by 5, if its unit's digit is 5 or 0. e.g. 895, 100
(v) By 6 - A number is divisible by 6, if it is divisible by both 2 and by 3. i.e. the
number should be an even number and the sum of its digits should be divisible by
3.
(vi) By 8 - A number is divisible by 8, if the last three digits of the number are Os
or are divisible by 8. As 1000 is divisible by 8, it is sufficient if the divisibility test
is restricted to the last three digits e.g. 135128, 45000
(vii) By 9 - A number is divisible by 9, if the sum of its digits is divisible by 9. e.g.
810, 92754
(viii) By 11-A number is divisible by 11, if the difference between the sum of the
digits at odd places and sum of the digits at even places of the number is either 0
or a multiple of 11.
e.g. 121, 65967. In the first case 1+1 -2 = 0. In the second case 6+9+7 = 22 and
5+6 = 11 and the difference is 11. Therefore, both these numbers are divisible by
11.
(ix) By 12-A number is divisible by 12, if it both divisible by 3 and by 4. i.e., the
sum of the digits should be divisible by 3 and the last two digits should be divisible
by 4. e.g. 144, 8136.
(x) By 15 - A number is divisible by 15, if it is divisible by both 5 and 3.
(xi) By 25-2358975 is divisible by 25 if the last two digits of 2358975 are divisible
by 25 or the last two digits are 0.
(xii) By 75 - A number is divisible by 75, if it is both divisible by 3 and by 25. i.e.
the sum of the digits should be divisible by 3 and the last two digits should be
divisible by 25.
(xiii) By 125 - A number is divisible by 125, if its last three right hand digits are
divisible by 125 or the last three digits are Os. e.g. 1254375, 12000
D. Properties of the numbers
Following are some properties of the numbers which are helpful in solving the
questions in the examination.
(i) The sum of 5 successive whole numbers is always divisible by 5.
(ii) The product of 3 consecutive natural numbers is divisible by 6.
(iii) The product of 3 consecutive natural numbers, the first of which is an even
number is divisible by 24.
(iv) The sum of a two-digit number and a number formed by reversing its digits is
divisible by 11. E.g. 28 +82 = 110, which is divisible by 11. At the same time, the
difference between those numbers will be divisible by 9. e.g. 82-28 54, which is
divisible by 9.
(v) n(n 1)
n , n
2
is the sum of first n natural numbers.
(vi) 2
2n(n 1)(2n 1)
n , n
6
is the sum of first n perfect squares.
7 Ekoching
Your door to future
then 2" - 1 is divisible by 3.
(iii) By 4 - A number is divisible by 4 when the last two digits of the number are
Os or are divisible by 4. As 100 is divisible by 4, it is sufficient if the divisibility test
is restricted to the last two digits. e.g. 145896, 128, 18400
(iv) By 5- A number is divisible by 5, if its unit's digit is 5 or 0. e.g. 895, 100
(v) By 6 - A number is divisible by 6, if it is divisible by both 2 and by 3. i.e. the
number should be an even number and the sum of its digits should be divisible by
3.
(vi) By 8 - A number is divisible by 8, if the last three digits of the number are Os
or are divisible by 8. As 1000 is divisible by 8, it is sufficient if the divisibility test
is restricted to the last three digits e.g. 135128, 45000
(vii) By 9 - A number is divisible by 9, if the sum of its digits is divisible by 9. e.g.
810, 92754
(viii) By 11-A number is divisible by 11, if the difference between the sum of the
digits at odd places and sum of the digits at even places of the number is either 0
or a multiple of 11.
e.g. 121, 65967. In the first case 1+1 -2 = 0. In the second case 6+9+7 = 22 and
5+6 = 11 and the difference is 11. Therefore, both these numbers are divisible by
11.
(ix) By 12-A number is divisible by 12, if it both divisible by 3 and by 4. i.e., the
sum of the digits should be divisible by 3 and the last two digits should be divisible
by 4. e.g. 144, 8136.
(x) By 15 - A number is divisible by 15, if it is divisible by both 5 and 3.
(xi) By 25-2358975 is divisible by 25 if the last two digits of 2358975 are divisible
by 25 or the last two digits are 0.
(xii) By 75 - A number is divisible by 75, if it is both divisible by 3 and by 25. i.e.
the sum of the digits should be divisible by 3 and the last two digits should be
divisible by 25.
(xiii) By 125 - A number is divisible by 125, if its last three right hand digits are
divisible by 125 or the last three digits are Os. e.g. 1254375, 12000
D. Properties of the numbers
Following are some properties of the numbers which are helpful in solving the
questions in the examination.
(i) The sum of 5 successive whole numbers is always divisible by 5.
(ii) The product of 3 consecutive natural numbers is divisible by 6.
(iii) The product of 3 consecutive natural numbers, the first of which is an even
number is divisible by 24.
(iv) The sum of a two-digit number and a number formed by reversing its digits is
divisible by 11. E.g. 28 +82 = 110, which is divisible by 11. At the same time, the
difference between those numbers will be divisible by 9. e.g. 82-28 54, which is
divisible by 9.
(v) n(n 1)
n , n
2
is the sum of first n natural numbers.
(vi) 2
2n(n 1)(2n 1)
n , n
6
is the sum of first n perfect squares.
7 Ekoching
Your door to future
(vii)
2
22
33n (n 1)
n n , n
4
is the sum of first n perfect cubes.
(viii) x
n
+ y
n
= (x + y) (x
n-1
-x
n-2
.y + x
n-3
y² -... +y
n-1
) when n is odd. Therefore, when
n is odd, x
n
+ y
n
is divisible by x + y.
e.g. 33 +2335 and is divisible by 5.
(ix) x
n
- y
n
= (x + y) (x
n-1
-x
n-2
y+... y
n-1
) when n is even. Therefore, when n is even,
x
n
- y
n
is divisible by x +y.
e.g. 7
2
-3
2
= 40, which is divisible by 10.
(x) x
n
-y
n
= (x-y) (x
n-1
+x
n-2
.y + ... + y
n-1
) for both odd and even n. Therefore,
x
n
- y
n
is divisible by x-y.
e.g. 9
4
-2
4
=6545 which is divisible by 7.
E. LCM & HCF
- In case of HCF, if some remainders are given, then first those remainders
are subtracted from the numbers given and then their HCF is calculated.
- Sometimes in case of HCF questions, the same remainder is required is
given and the remainder is not given. In such questions, the answer is the
HCF of the difference of the numbers taken in pairs.
- In case of LCM, if a single remainder is given, then firstly the LCM is
calculated and then that single reminder is added in that.
- In case of LCM, if for different numbers different remainders are given, then
the difference between the number and its respective remainder will be
equal. In that case, firstly the LCM is calculated, then that common
difference between the number and its respective remainder is subtracted
from that.
LCM and HCF of Fractions
LCM of fractions = LCM of numerators
;
HCF of denominators
e.g. LCM of 3 1 3 (LCM of numerators)
and
4 2 2(HCF of denominators)
HCF of fractions = HCF of numerators
LCM of denominators
e.g. HCF of 3 1 1(HCF of numerators)
and
4 2 4(LCM of denominators)
Note that the product of the two fractions is always equal to the product of LCM
and HCF of the two fractions.
The product of the two fractions 3 1 3
.
4 2 8
The product of the LCM and HCF 3 1 3
.
2 4 8
F. Fractions
Numbers of the form 3/4, 4/5, are called fractions. A fraction can be written as p/q
where q = 0.
- If the numerator and denominator of a fraction are multiplied/ divided by
the same number then the value of the fraction does not change. 8 Ekoching
Your door to future
2
22
33n (n 1)
n n , n
4
is the sum of first n perfect cubes.
(viii) x
n
+ y
n
= (x + y) (x
n-1
-x
n-2
.y + x
n-3
y² -... +y
n-1
) when n is odd. Therefore, when
n is odd, x
n
+ y
n
is divisible by x + y.
e.g. 33 +2335 and is divisible by 5.
(ix) x
n
- y
n
= (x + y) (x
n-1
-x
n-2
y+... y
n-1
) when n is even. Therefore, when n is even,
x
n
- y
n
is divisible by x +y.
e.g. 7
2
-3
2
= 40, which is divisible by 10.
(x) x
n
-y
n
= (x-y) (x
n-1
+x
n-2
.y + ... + y
n-1
) for both odd and even n. Therefore,
x
n
- y
n
is divisible by x-y.
e.g. 9
4
-2
4
=6545 which is divisible by 7.
E. LCM & HCF
- In case of HCF, if some remainders are given, then first those remainders
are subtracted from the numbers given and then their HCF is calculated.
- Sometimes in case of HCF questions, the same remainder is required is
given and the remainder is not given. In such questions, the answer is the
HCF of the difference of the numbers taken in pairs.
- In case of LCM, if a single remainder is given, then firstly the LCM is
calculated and then that single reminder is added in that.
- In case of LCM, if for different numbers different remainders are given, then
the difference between the number and its respective remainder will be
equal. In that case, firstly the LCM is calculated, then that common
difference between the number and its respective remainder is subtracted
from that.
LCM and HCF of Fractions
LCM of fractions = LCM of numerators
;
HCF of denominators
e.g. LCM of 3 1 3 (LCM of numerators)
and
4 2 2(HCF of denominators)
HCF of fractions = HCF of numerators
LCM of denominators
e.g. HCF of 3 1 1(HCF of numerators)
and
4 2 4(LCM of denominators)
Note that the product of the two fractions is always equal to the product of LCM
and HCF of the two fractions.
The product of the two fractions 3 1 3
.
4 2 8
The product of the LCM and HCF 3 1 3
.
2 4 8
F. Fractions
Numbers of the form 3/4, 4/5, are called fractions. A fraction can be written as p/q
where q = 0.
- If the numerator and denominator of a fraction are multiplied/ divided by
the same number then the value of the fraction does not change. 8 Ekoching
Your door to future
- For any positive proper fraction p/q (p<q), the value of the fraction
increases when both the denominator and numerator are added by the
same positive number.
e.g 3 3 1 4
0.75, 0.8.
4 4 1 5
- For any positive proper fraction p/q (p<q), the value of the fraction
decreases when both the numerator and denominator are subtracted by
the same positive number.
e.g 3 3 1 2
0.75, 0.67
4 4 1 3
- For any positive improper fraction p/q (p>q), the value of the fraction
decreases when both the 5 numerator and the denominator are added to
the same positive. E.g. 5
1.25
4
adding 1 to the numerator and the
denominator, we get 5 1 6
1.2.
4 1 5
Which is less than 1.25.
- For any positive improper fraction p/q (p>q), the value of the fraction
increases when both the numerator and denominator are subtracted by the
same positive number. E.g. = 5
1.25
4
, by subtracting 1 from both the
numerator and denominator we get, 5 1 4
1.33 1.25.
4 1 3
Types of fractions
Common Fractions: Fractions such 3/4, 32/43 etc are called common or vulgar
fractions.
Decimal Fractions: Fractions whose denominators are 10, 100, 1000, ... are called
decimal fractions.
Proper Fraction: A fraction whose numerator is less than its denominator is known
as a proper fraction e.g..3/4
Improper Fraction: A fraction whose numerator is greater than its denominator is
known as an improper fraction. e.g. 4/3
Mixed Fractions: Fractions which consists of an integral part and a fractional part
are called mixed fractions. All improper fractions can be expressed as mixed
fractions and vice versa. e.g. 3
1
4 .
Recurring Decimals: A decimal in which a set of figures is repeated continually is
called a recurring or periodic or a circulating decimal.
e.g. 1
0.142857
7
..... the dots indicate that the figure between 1 and 7 will repeat
continuously.
G. Indices
The expression 5
a a a a a a
Similarly for any positive integer n, n
a a a a .......n times.
In a
n
, a is called the base and n is called the index.
Law of Indices
Let m and n be positive integers, then
(i) m n m n
a a a
9 Ekoching
Your door to future
increases when both the denominator and numerator are added by the
same positive number.
e.g 3 3 1 4
0.75, 0.8.
4 4 1 5
- For any positive proper fraction p/q (p<q), the value of the fraction
decreases when both the numerator and denominator are subtracted by
the same positive number.
e.g 3 3 1 2
0.75, 0.67
4 4 1 3
- For any positive improper fraction p/q (p>q), the value of the fraction
decreases when both the 5 numerator and the denominator are added to
the same positive. E.g. 5
1.25
4
adding 1 to the numerator and the
denominator, we get 5 1 6
1.2.
4 1 5
Which is less than 1.25.
- For any positive improper fraction p/q (p>q), the value of the fraction
increases when both the numerator and denominator are subtracted by the
same positive number. E.g. = 5
1.25
4
, by subtracting 1 from both the
numerator and denominator we get, 5 1 4
1.33 1.25.
4 1 3
Types of fractions
Common Fractions: Fractions such 3/4, 32/43 etc are called common or vulgar
fractions.
Decimal Fractions: Fractions whose denominators are 10, 100, 1000, ... are called
decimal fractions.
Proper Fraction: A fraction whose numerator is less than its denominator is known
as a proper fraction e.g..3/4
Improper Fraction: A fraction whose numerator is greater than its denominator is
known as an improper fraction. e.g. 4/3
Mixed Fractions: Fractions which consists of an integral part and a fractional part
are called mixed fractions. All improper fractions can be expressed as mixed
fractions and vice versa. e.g. 3
1
4 .
Recurring Decimals: A decimal in which a set of figures is repeated continually is
called a recurring or periodic or a circulating decimal.
e.g. 1
0.142857
7
..... the dots indicate that the figure between 1 and 7 will repeat
continuously.
G. Indices
The expression 5
a a a a a a
Similarly for any positive integer n, n
a a a a .......n times.
In a
n
, a is called the base and n is called the index.
Law of Indices
Let m and n be positive integers, then
(i) m n m n
a a a
9 Ekoching
Your door to future
(ii)
n
m mn
aa
(iii) m
mn
n
a
a
a
, where a0
(iv) m m m
(ab) a b
(v) 0
a1 , where a0
(vi) n
n
1
a
a
(vii) p
qpq
aa i.e. the q
th
root of a raised to the power of p.
(viii) In particular , 1
qq
aa
H. Remainder Theory
Questions from number system appear regularly in almost all competitive exams.
Within number system, the questions on remainders are found to be most tricky.
This will help you learn different types of remainder questions and various
approaches you can apply to solve these.
The basic remainder formula is:
Dividend = Divisor Quotient + Remainder
If remainder = 0, then it the number is perfectly divisible by divisor and divisor is
a factor of the number e.g. when 8 divides 40, the remainder is 0, it can be said that
8 is a factor of 40.
There are few important results relating to numbers. Those will be covered one
by one in the following examples.
(i) Formulas Based Concepts for Remainder:
(a"+b") is divisible by (a + b), when n is odd.
(a"-b") is divisible by (a + b), when n is even.
(a"-b") is always divisible by (a - b), for every n.
(ii) Concept of Negative Remainder:
By definition, remainder cannot be negative. But in certain cases, you can
assume that for your convenience. But a negative remainder in real sense
means that you need to add the divisor in the negative remainder to find
the real remainder.
NOTE: Whenever you are getting a negative number as the remainder,
make it positive by adding the divisor to the negative remainder.
(iii) Cyclicity in Remainders:
Cyclicity is the property of remainders, due to which they start repeating
themselves after a certain point.
(iv) Role of Euler's Number in Remainders:
Euler's Remainder theorem states that, for co-prime numbers M and N,
Remainder [MEN)/N] = 1, i.e. number M raised to Euler number of N will
leave a remainder 1 when divided by N. Always check whether the
numbers are co-primes are not as Euler's theorem is applicable only for co-
prime numbers.
(iv) Wilson theorem:
If p is a prime number, then (p 1)! will give remainder as p1 when divide
by p and similarly (p 2)! will give remainder as 1 when divide by p 10 Ekoching
Your door to future
n
m mn
aa
(iii) m
mn
n
a
a
a
, where a0
(iv) m m m
(ab) a b
(v) 0
a1 , where a0
(vi) n
n
1
a
a
(vii) p
qpq
aa i.e. the q
th
root of a raised to the power of p.
(viii) In particular , 1
aa
H. Remainder Theory
Questions from number system appear regularly in almost all competitive exams.
Within number system, the questions on remainders are found to be most tricky.
This will help you learn different types of remainder questions and various
approaches you can apply to solve these.
The basic remainder formula is:
Dividend = Divisor Quotient + Remainder
If remainder = 0, then it the number is perfectly divisible by divisor and divisor is
a factor of the number e.g. when 8 divides 40, the remainder is 0, it can be said that
8 is a factor of 40.
There are few important results relating to numbers. Those will be covered one
by one in the following examples.
(i) Formulas Based Concepts for Remainder:
(a"+b") is divisible by (a + b), when n is odd.
(a"-b") is divisible by (a + b), when n is even.
(a"-b") is always divisible by (a - b), for every n.
(ii) Concept of Negative Remainder:
By definition, remainder cannot be negative. But in certain cases, you can
assume that for your convenience. But a negative remainder in real sense
means that you need to add the divisor in the negative remainder to find
the real remainder.
NOTE: Whenever you are getting a negative number as the remainder,
make it positive by adding the divisor to the negative remainder.
(iii) Cyclicity in Remainders:
Cyclicity is the property of remainders, due to which they start repeating
themselves after a certain point.
(iv) Role of Euler's Number in Remainders:
Euler's Remainder theorem states that, for co-prime numbers M and N,
Remainder [MEN)/N] = 1, i.e. number M raised to Euler number of N will
leave a remainder 1 when divided by N. Always check whether the
numbers are co-primes are not as Euler's theorem is applicable only for co-
prime numbers.
(iv) Wilson theorem:
If p is a prime number, then (p 1)! will give remainder as p1 when divide
by p and similarly (p 2)! will give remainder as 1 when divide by p 10 Ekoching
Your door to future
4. Average
Average means Arithmetic mean of the items and it is = Sum of Items
Number of Items
When the difference between all the items is same, then average is equal to n1
2
item, where n is the total number of items.
Average speed: If a man covers some journey from A to B at u km/hr. and returns
back to A at B 2uv uniform speed of v km/hr., then the average speed during the
whole journey is 2uv
uv km/hr
(i) If x is added in all the items, then average increases by x.
(ii) If x is subtracted from all the items, then average decreases by x.
(iii) If every item is multiplied by x, then average also gets multiplied by x.
(iv) If every item is divided by x, then average also gets divided by x.
(v) Weighted average 1 1 2 2 n n
1 2 n
a x a x ...a x
a a ....... a
5. Basic Algebra
A. Algebraic Formulae
(i) x
n
+ y
n
= (x+ y)(x
n-1
-x
n-2
y + x
n-3
y² - .. + y
n-1
) when n is odd. When n is odd,
x
n
+ y
n
is divisible by x + y
(ii) n n n 1 n 2 n 1
x y (x y)(x x y )
when n is even. When n is even, nn
xy
is divisible by x + y.
(iii) n n n 1 n 2 n 1
x y (x y)(x x y .... y )
for both odd and even n.
Therefore, nn
xy is divisible by x – y.
(iv) (a + b)²=a
2
+ b²+2ab.
(v) (a - b)²=a
2
+ b² - 2ab.
(vi) (a
2
– b
2
) = (a + b) (a - b).
(vii) (a + b)2- (a - b)² = 4ab.
(viii) (a + b)² + (a - b)² = 2(a² + b²).
(ix) (a + b)
3
= a + b³ + 3ab(a + b).
(x) (a - b)
3
= a-b³-3ab(a - b).
(xi) (a
3
+ b
3
) = (a + b)(a² + b² - ab).
(xii) (a
3
– b
3
) = (a - b) (a² + b² + ab).
(xiii) (a+b+c)² = [a² + b² + c² + 2(ab + bc + ca)].
(xiv) 3 3 2 2 2
(a3 b c 3abc) (a b c)(a b c ab bc ca) . If 33
a b c 0 a b c 3abc
(xv) 2
(x a)(x b) x (a b)x ab.
B. Linear Equations:
Consider two linear equations: 1 1 1
2 2 2
A x B y C
A x B y C
This pair of linear equations has: 11 Ekoching
Your door to future
Average means Arithmetic mean of the items and it is = Sum of Items
Number of Items
When the difference between all the items is same, then average is equal to n1
2
item, where n is the total number of items.
Average speed: If a man covers some journey from A to B at u km/hr. and returns
back to A at B 2uv uniform speed of v km/hr., then the average speed during the
whole journey is 2uv
uv km/hr
(i) If x is added in all the items, then average increases by x.
(ii) If x is subtracted from all the items, then average decreases by x.
(iii) If every item is multiplied by x, then average also gets multiplied by x.
(iv) If every item is divided by x, then average also gets divided by x.
(v) Weighted average 1 1 2 2 n n
1 2 n
a x a x ...a x
a a ....... a
5. Basic Algebra
A. Algebraic Formulae
(i) x
n
+ y
n
= (x+ y)(x
n-1
-x
n-2
y + x
n-3
y² - .. + y
n-1
) when n is odd. When n is odd,
x
n
+ y
n
is divisible by x + y
(ii) n n n 1 n 2 n 1
x y (x y)(x x y )
when n is even. When n is even, nn
xy
is divisible by x + y.
(iii) n n n 1 n 2 n 1
x y (x y)(x x y .... y )
for both odd and even n.
Therefore, nn
xy is divisible by x – y.
(iv) (a + b)²=a
2
+ b²+2ab.
(v) (a - b)²=a
2
+ b² - 2ab.
(vi) (a
2
– b
2
) = (a + b) (a - b).
(vii) (a + b)2- (a - b)² = 4ab.
(viii) (a + b)² + (a - b)² = 2(a² + b²).
(ix) (a + b)
3
= a + b³ + 3ab(a + b).
(x) (a - b)
3
= a-b³-3ab(a - b).
(xi) (a
3
+ b
3
) = (a + b)(a² + b² - ab).
(xii) (a
3
– b
3
) = (a - b) (a² + b² + ab).
(xiii) (a+b+c)² = [a² + b² + c² + 2(ab + bc + ca)].
(xiv) 3 3 2 2 2
(a3 b c 3abc) (a b c)(a b c ab bc ca) . If 33
a b c 0 a b c 3abc
(xv) 2
(x a)(x b) x (a b)x ab.
B. Linear Equations:
Consider two linear equations: 1 1 1
2 2 2
A x B y C
A x B y C
This pair of linear equations has: 11 Ekoching
Your door to future
(i) A unique solution if, 11
22
AB
.
AB
(ii) Infinite solutions if, 111
222
A B C
.
A B C
(iii) No Solutions if, 1 1 1
2 2 2
A B C
.
A B C
C. Quadratic Equations:
(i) General form of a quadratic equation 2
ax bx c 0,a 0
(ii) The discriminant of a quadratic equation is 2
D b 4ac
(iii) The roots of the above quadratic equation are b D b D
and
2a 2a
(iv) Let and be the roots of the above quadratic equation. If D > 0, then
the roots are real and unequal. The sum of the roots b
a
and the
product c
a
(v) If D is a perfect square, then the roots are rational and unequal.
(vi) If D = 0, then the roots are real and equal and is equal to b
2a
(vii) If D < 0, then the roots are complex and unequal. If a, b and c of the
quadratic equation are rational, then the roots are conjugates of each other.
Ex. If p qi , then p qi
(viii) If D0 , then, 2
ax bx c a(x a)(x ).
(ix) If c = a, then the roots are reciprocal.
(x) If b = 0, then the roots are equal in magnitude but opposite in sign.
(xi) If one of the roots of a quadratic equation with rational coefficients is
irrational, then the other roots must be irrational conjugate. If p q, then p q.
(xii) If , are the roots of a quadratic equation, then the equation is 2
x (a )x 0.
(xiii) The minimum(if a0 ) or maximum(if a0 ) value of a quadratic equation
of 2
y ax bx c is D
4a
, occurs at b
x
2a
, where D = discriminant 2
b 4ac.
D. Inequalities
(i) Inequalities, Interval Notations and Graphs
Inequality Interval Notation Graph a x b
[a, b]
a x b
(a, b]
a x b
[a, b)
12 Ekoching
Your door to future
22
AB
.
AB
(ii) Infinite solutions if, 111
222
A B C
.
A B C
(iii) No Solutions if, 1 1 1
2 2 2
A B C
.
A B C
C. Quadratic Equations:
(i) General form of a quadratic equation 2
ax bx c 0,a 0
(ii) The discriminant of a quadratic equation is 2
D b 4ac
(iii) The roots of the above quadratic equation are b D b D
and
2a 2a
(iv) Let and be the roots of the above quadratic equation. If D > 0, then
the roots are real and unequal. The sum of the roots b
a
and the
product c
a
(v) If D is a perfect square, then the roots are rational and unequal.
(vi) If D = 0, then the roots are real and equal and is equal to b
2a
(vii) If D < 0, then the roots are complex and unequal. If a, b and c of the
quadratic equation are rational, then the roots are conjugates of each other.
Ex. If p qi , then p qi
(viii) If D0 , then, 2
ax bx c a(x a)(x ).
(ix) If c = a, then the roots are reciprocal.
(x) If b = 0, then the roots are equal in magnitude but opposite in sign.
(xi) If one of the roots of a quadratic equation with rational coefficients is
irrational, then the other roots must be irrational conjugate. If p q, then p q.
(xii) If , are the roots of a quadratic equation, then the equation is 2
x (a )x 0.
(xiii) The minimum(if a0 ) or maximum(if a0 ) value of a quadratic equation
of 2
y ax bx c is D
4a
, occurs at b
x
2a
, where D = discriminant 2
b 4ac.
D. Inequalities
(i) Inequalities, Interval Notations and Graphs
Inequality Interval Notation Graph a x b
[a, b]
a x b
(a, b]
a x b
[a, b)
12 Ekoching
Your door to future
a < x < b (a, b)
x b,x b
( , b]
x b,x b
( , b)
a x ,x a
[a, )
a x ,x a
(a, )
(i) If a > b, then b < a. (iii) If a > b, then a b > 0 or b - a<0.
(iv) If a> b, then a + c > b + c. (v) If a> b, then a-c>b-c.
(vi)If a > b and c >d, then a +c > b+d. (vii) If a > b and c >d, then a-d>b-c.
(viii) If a > b and m> 0, then ma > mb. (ix)If a > b and m> 0, then ab
.
mm
(x) If a > b and m > 0, then ma > mb. (xi) If a > b and m < 0, then ab
.
mm
(xii)If 0 < a < b and n > 0, then an < bn. (xiii)If 0<a< b and n < o, then an > bn.
(xiv) If 0 < a < b, then nn
ab
(xv) ab
ab
2
, where a > 0, b > 0; an equality is valid only if a = b.
(xvi)1
a 2,
a
where a > o; an equality taken place only at a = 1.
(xvii) 1 2 nn
1 2 n
a a .... a
a a ....a
n
, where a1, a2, …… ,a
n
> 0.
(xviii) If ax + b > 0 and a > 0, then x > b
.
a
(xix) If ax + b > 0 and a > 0, then x < b
.
a
(xx) a b a b .
(xxi) If x a, then – a < x < a, where a > 0.
(xxii) If x a, then x < -a and x > a, where a > 0.
(xxiii) If x
2
< a, then xa , where a > 0.
(xxiv) If 2
xa , then xa , where a > 0.
E. Arithmetic and Geometric Progression
Arithmetic Progression:
An arithmetic progression is a sequence of numbers in which each term is derived
from the preceding term by adding or subtracting a fixed number called the
common difference e.g. The sequence 9,6,3,0,-3, is an arithmetic progression with
-3 as the common difference. The progression -3, 0, 3, 6, 9 is an Arithmetic
Progression (AP) with 3 as the common difference. 13 Ekoching
Your door to future
x b,x b
( , b]
x b,x b
( , b)
a x ,x a
[a, )
a x ,x a
(a, )
(i) If a > b, then b < a. (iii) If a > b, then a b > 0 or b - a<0.
(iv) If a> b, then a + c > b + c. (v) If a> b, then a-c>b-c.
(vi)If a > b and c >d, then a +c > b+d. (vii) If a > b and c >d, then a-d>b-c.
(viii) If a > b and m> 0, then ma > mb. (ix)If a > b and m> 0, then ab
.
mm
(x) If a > b and m > 0, then ma > mb. (xi) If a > b and m < 0, then ab
.
mm
(xii)If 0 < a < b and n > 0, then an < bn. (xiii)If 0<a< b and n < o, then an > bn.
(xiv) If 0 < a < b, then nn
ab
(xv) ab
ab
2
, where a > 0, b > 0; an equality is valid only if a = b.
(xvi)1
a 2,
a
where a > o; an equality taken place only at a = 1.
(xvii) 1 2 nn
1 2 n
a a .... a
a a ....a
n
, where a1, a2, …… ,a
n
> 0.
(xviii) If ax + b > 0 and a > 0, then x > b
.
a
(xix) If ax + b > 0 and a > 0, then x < b
.
a
(xx) a b a b .
(xxi) If x a, then – a < x < a, where a > 0.
(xxii) If x a, then x < -a and x > a, where a > 0.
(xxiii) If x
2
< a, then xa , where a > 0.
(xxiv) If 2
xa , then xa , where a > 0.
E. Arithmetic and Geometric Progression
Arithmetic Progression:
An arithmetic progression is a sequence of numbers in which each term is derived
from the preceding term by adding or subtracting a fixed number called the
common difference e.g. The sequence 9,6,3,0,-3, is an arithmetic progression with
-3 as the common difference. The progression -3, 0, 3, 6, 9 is an Arithmetic
Progression (AP) with 3 as the common difference. 13 Ekoching
Your door to future
• The general form of an Arithmetic Progression is a, a +d, a + 2d, a + 3d and
so on. Thus nth term of an AP series is T, = a + (n-1) d. Where T, = nth term
and a = first term. Here d = common difference = n n 1T T .
• Sometimes the last term is given and either 'd' is asked or 'a' is asked.
Then formula becomes = a + (n-1) d
• There is another formula, applied to find the sum of first n terms of an AP:
S, n/2[2a+(n-1)d]
• The sum of n terms is also equal to the formula S, n/2(a+I) where is the
last term.
• When three quantities are in AP, the middle one is called as the arithmetic
mean of the other two. If a, b and c are three terms in AP then
b = (a + c)/2.
Geometric Progression:
A geometric progression is a sequence in which each term is derived by
multiplying or dividing the preceding term by a fixed number called the common
ratio. The sequence 4, -2, 1, 2,.. is a Geometric Progression (GP) for which - ½ is
the common ratio.
- The general form of a GP is a, ar, ar², ar
3
and so on.
- Thus nth term of a GP series is T, = ar, where a = first term and r =
common ratio = Tm/Tm-1
- The formula applied to calculate sum of first n terms of a GP: Sn = a(r"-1)/r-
1 where [r] 1 and Sa(1 r")/1 r where [r] 1 .
- When three quantities are in GP, the middle one is called as the geometric
mean of the other two. If a, b and c are three quantities in GP and b is the
geometric mean of a and c i.e. b ac
- The sum of infinite terms of a GP series nS a /1 r
F. Special Equations
• If ax by k
Factors of k Both a,b Only a/only b None of a,b
Example 2x 3y 36 5x 13y 1000 3x 7y 115
Number of positive integer
solutions k
17
ab
k
1 16
ab
kk
1or
ab ab
Here answer=6
Number of non-negative
integer solutions k
16
ab
k
15
ab
kk
1 or
ab ab
Here answer=6
Where [x] is the greatest integer less than or equal to x
G. Cauchy’s functional equations
• In functional equations, functions themselves are unknowns, then the
following formulae will help you derive the expressions for functions.
- if f(x y) f(x) f(y) then f(x) kx 14 Ekoching
Your door to future
so on. Thus nth term of an AP series is T, = a + (n-1) d. Where T, = nth term
and a = first term. Here d = common difference = n n 1T T .
• Sometimes the last term is given and either 'd' is asked or 'a' is asked.
Then formula becomes = a + (n-1) d
• There is another formula, applied to find the sum of first n terms of an AP:
S, n/2[2a+(n-1)d]
• The sum of n terms is also equal to the formula S, n/2(a+I) where is the
last term.
• When three quantities are in AP, the middle one is called as the arithmetic
mean of the other two. If a, b and c are three terms in AP then
b = (a + c)/2.
Geometric Progression:
A geometric progression is a sequence in which each term is derived by
multiplying or dividing the preceding term by a fixed number called the common
ratio. The sequence 4, -2, 1, 2,.. is a Geometric Progression (GP) for which - ½ is
the common ratio.
- The general form of a GP is a, ar, ar², ar
3
and so on.
- Thus nth term of a GP series is T, = ar, where a = first term and r =
common ratio = Tm/Tm-1
- The formula applied to calculate sum of first n terms of a GP: Sn = a(r"-1)/r-
1 where [r] 1 and Sa(1 r")/1 r where [r] 1 .
- When three quantities are in GP, the middle one is called as the geometric
mean of the other two. If a, b and c are three quantities in GP and b is the
geometric mean of a and c i.e. b ac
- The sum of infinite terms of a GP series nS a /1 r
F. Special Equations
• If ax by k
Factors of k Both a,b Only a/only b None of a,b
Example 2x 3y 36 5x 13y 1000 3x 7y 115
Number of positive integer
solutions k
17
ab
k
1 16
ab
kk
1or
ab ab
Here answer=6
Number of non-negative
integer solutions k
16
ab
k
15
ab
kk
1 or
ab ab
Here answer=6
Where [x] is the greatest integer less than or equal to x
G. Cauchy’s functional equations
• In functional equations, functions themselves are unknowns, then the
following formulae will help you derive the expressions for functions.
- if f(x y) f(x) f(y) then f(x) kx 14 Ekoching
Your door to future
- if f(x y) f(x)f(y) then x
f(x) k
- if f(xy) f(x) f(y) then xf(x) log k
- if f(xy) f(x)f(y) then k
f(x) x
- if 11
f(x)f f(x) f
xx
then k
f(x) x 1
6. Percentage & Profit Loss
A. Percentage
To Increase a Number by x %:
If a number is increased by 10%, then it becomes 1.1 times of itself.
If a number is increased by 20%, then it becomes 1.2 times of itself.
If a number is increased by 30 %, then it becomes 1.3 times of itself.
If a number is increased by 40%, then it becomes 1.4 times of itself.
To Decrease a Number by x %:
If a number is decreased by 10%, then it becomes 0.90 times of itself.
If a number is decreased by 20 %, then it becomes 0.80 times of itself.
If a number is decreased by 30 %, then it becomes 0.70 times of itself.
If a number is decreased by 40%, then it becomes 0.60 times of itself.
Salary/Weight/Income More.
If A's income is R % more than B, then B is income is less than that of A by R
100 %.
100 R
Given below are some of the important result in that context
Salary/Weight/Income Less.
If A's income is R% less than B, then B's income is more than that of A byR
100 %.
100 R
Given below are some important result in that context.
If A is 2
16 %
3 less than B, the B is 20 % more than A.
If A is 20 % less than B, then is 25 % more than A.
If A is 25 % less than B, than B is 1
33 %
3 more than A.
If the price is increased then consumption should be decreased by 100 R
(100 R)
If the price is decreased, then consumption should be increased
by 100 R
(100 R)
Increase and Decrease by the same % age.
If a number is increased by R %, then this number is decreased by R %, then
in total there would be a decrease of 2
R
%.
100
Increase and Decrease by different% age.
If a number is decreased by X %, then this is again increased by Y %. Then
the total increase in the no. will be X + Y + XY
.
100 15 Ekoching
Your door to future
f(x) k
- if f(xy) f(x) f(y) then xf(x) log k
- if f(xy) f(x)f(y) then k
f(x) x
- if 11
f(x)f f(x) f
xx
then k
f(x) x 1
6. Percentage & Profit Loss
A. Percentage
To Increase a Number by x %:
If a number is increased by 10%, then it becomes 1.1 times of itself.
If a number is increased by 20%, then it becomes 1.2 times of itself.
If a number is increased by 30 %, then it becomes 1.3 times of itself.
If a number is increased by 40%, then it becomes 1.4 times of itself.
To Decrease a Number by x %:
If a number is decreased by 10%, then it becomes 0.90 times of itself.
If a number is decreased by 20 %, then it becomes 0.80 times of itself.
If a number is decreased by 30 %, then it becomes 0.70 times of itself.
If a number is decreased by 40%, then it becomes 0.60 times of itself.
Salary/Weight/Income More.
If A's income is R % more than B, then B is income is less than that of A by R
100 %.
100 R
Given below are some of the important result in that context
Salary/Weight/Income Less.
If A's income is R% less than B, then B's income is more than that of A byR
100 %.
100 R
Given below are some important result in that context.
If A is 2
16 %
3 less than B, the B is 20 % more than A.
If A is 20 % less than B, then is 25 % more than A.
If A is 25 % less than B, than B is 1
33 %
3 more than A.
If the price is increased then consumption should be decreased by 100 R
(100 R)
If the price is decreased, then consumption should be increased
by 100 R
(100 R)
Increase and Decrease by the same % age.
If a number is increased by R %, then this number is decreased by R %, then
in total there would be a decrease of 2
R
%.
100
Increase and Decrease by different% age.
If a number is decreased by X %, then this is again increased by Y %. Then
the total increase in the no. will be X + Y + XY
.
100 15 Ekoching
Your door to future
B. Simple Interest and Compound Interest
Simple Interest = P R T
100
, where, P is the amount invested or
borrowed, T is the time in years and R is the annual interest rate.
A P SI , where, A is the amount payable or receivable at the end of
period T, P is the principal and SI is the simple interest.
A P(1 R/100)", where, A is the amount receivable on compound
interest basis, P is the principal invested, R is the annual rate of interest
and n is the number of years for which the sum has been invested.
Compound Interest = A-P, where, C.I is the compound interest, A is the
amount receivable with interest and P is the principal invested.
Interest rate on monthly instalment plans
R = 24XIX100/N(F+L), where, R is the interest, I is the instalment, N is the
number of instalments, F is the principal left before the first instalment and L is
the principal left before last instalment.
Equated Instalment n
AR
X
100100
1
100 R
where,
X is the equated installment, A is the amount borrowed, R is the rate of interest and n is
the number of years.
A = P(1+R/200)
2N
, if the interest is calculated half-yearly.
A = P(1+R/400)
4N
, if the interest is calculated quarterly.
Rule of 72 - Time taken to double one's investment can be obtained by dividing 72 by the
interest rate. This is only in case of compound interest.
Rule of 69 - This rule is also used to determine the time taken to double one's investment.
However, it is a more refined formula. Time taken = 0.35+ (69/Interest rate). This is also
true in case of compound interest only.
If D is the difference in Cl and SI for 2 years, and R is the rate of interest and P the principal
then, D=R/100R/100XP
The following table lists the values of an initial investment, P = Re. 1 for certain time
periods and rates of interest, calculated at both, simple and compound interest. This
would be of great help in time. Management during the paper, if memorized.
Time Rate 5% 10 % 20% 30%
SI CI SI CI SI CI SI CI
1 year 1.05 1.05 1.1 1.1 1.2 1.2 1.3 1.3
2 Yrs 1.10 1.1025 1.2 1.21 1.4 1.44 1.6 1.69
3 yrs 1.15 1.1575 1.3 1.331 1.6 1.728 1.9 2.197
4 yrs 1.4 1.4641 1.8 2.0736
16 Ekoching
Your door to future
Simple Interest = P R T
100
, where, P is the amount invested or
borrowed, T is the time in years and R is the annual interest rate.
A P SI , where, A is the amount payable or receivable at the end of
period T, P is the principal and SI is the simple interest.
A P(1 R/100)", where, A is the amount receivable on compound
interest basis, P is the principal invested, R is the annual rate of interest
and n is the number of years for which the sum has been invested.
Compound Interest = A-P, where, C.I is the compound interest, A is the
amount receivable with interest and P is the principal invested.
Interest rate on monthly instalment plans
R = 24XIX100/N(F+L), where, R is the interest, I is the instalment, N is the
number of instalments, F is the principal left before the first instalment and L is
the principal left before last instalment.
Equated Instalment n
AR
X
100100
1
100 R
where,
X is the equated installment, A is the amount borrowed, R is the rate of interest and n is
the number of years.
A = P(1+R/200)
2N
, if the interest is calculated half-yearly.
A = P(1+R/400)
4N
, if the interest is calculated quarterly.
Rule of 72 - Time taken to double one's investment can be obtained by dividing 72 by the
interest rate. This is only in case of compound interest.
Rule of 69 - This rule is also used to determine the time taken to double one's investment.
However, it is a more refined formula. Time taken = 0.35+ (69/Interest rate). This is also
true in case of compound interest only.
If D is the difference in Cl and SI for 2 years, and R is the rate of interest and P the principal
then, D=R/100R/100XP
The following table lists the values of an initial investment, P = Re. 1 for certain time
periods and rates of interest, calculated at both, simple and compound interest. This
would be of great help in time. Management during the paper, if memorized.
Time Rate 5% 10 % 20% 30%
SI CI SI CI SI CI SI CI
1 year 1.05 1.05 1.1 1.1 1.2 1.2 1.3 1.3
2 Yrs 1.10 1.1025 1.2 1.21 1.4 1.44 1.6 1.69
3 yrs 1.15 1.1575 1.3 1.331 1.6 1.728 1.9 2.197
4 yrs 1.4 1.4641 1.8 2.0736
16 Ekoching
Your door to future
C. Profit and Loss
Cost Price (CP):The price paid to buy a particular product is called its cost price.
Some overhead expenses such as transportation, taxes etc. are also included in the
cost price.
Selling Price (SP): The sum of money received for the product.
Marked Price (MP): The price that is listed or marked on the product. This is also
known as printed price/quotation price/invoice price/catalogue price.
Profit: There is a gain in a transaction if the selling price is more than the cost price.
The excess of the selling price to the cost price is called profit.
PROFIT = SELLING PRICE-COST PRICE
Loss: When the selling price is less than the cost price there is loss in the
transaction. The excess of cost price over the selling price is called loss.
• Loss = Cost Price - Selling Price
• % Profit = 100 x Profit/Cost Price
• % Loss = 100 x Loss/Cost price
Equal % profit & loss on the same selling price of two articles:
If two items are sold each at Rs X, one at a gain of p % and the other at a loss of p
%, then the two transactions have resulted in an overall loss of 2
p
%
100 , and the
absolute value of the loss is = Rs. 2
22
2.p .X
100 p
Equal % profit & loss on the same cost price of two articles:
If the cost price of two items is X, and one is sold at a profit of p % and the other at
a loss of p %, then the two transactions have resulted in no gain or no loss.
Trade Discount: To attract customers, it is a common practice to announce
discount on the marked price of an article.
Note: The discount is always taken as a % of the marked price, unless otherwise
specified.
E.g. Let the list price of an article be Rs. 450. A discount of 5% on its list price is
announced. Then, the new selling price = 450 x 95/100 = Rs 422.5.
Cash Discount: In addition to trade discount, the manufacturer may offer an
additional discount called the Cash Discount if the buyer makes full payment
within a certain specified time. Cash Discount is usually offered on the net price
(the price after subtracting discount from the marked price). Therefore, Cash
Price = Net Price - Cash Discount
Note: Cash discount is always calculated on net price, unless otherwise specified.
Wrong Weight: When a tradesman claims to sell at cost price, but uses a false
weight, then the percentage profit earned 100 Error
True weight Error
Successive Discounts: When a tradesman offers more than one discount to the
customer, then the total discount offered is calculated by applying the method of
decimals learned in the topic of percentage.
Example: A tradesman offers two successive discounts of 20 % and 10%. Calculate
the gross discount offered by the tradesman. 17 Ekoching
Your door to future
Cost Price (CP):The price paid to buy a particular product is called its cost price.
Some overhead expenses such as transportation, taxes etc. are also included in the
cost price.
Selling Price (SP): The sum of money received for the product.
Marked Price (MP): The price that is listed or marked on the product. This is also
known as printed price/quotation price/invoice price/catalogue price.
Profit: There is a gain in a transaction if the selling price is more than the cost price.
The excess of the selling price to the cost price is called profit.
PROFIT = SELLING PRICE-COST PRICE
Loss: When the selling price is less than the cost price there is loss in the
transaction. The excess of cost price over the selling price is called loss.
• Loss = Cost Price - Selling Price
• % Profit = 100 x Profit/Cost Price
• % Loss = 100 x Loss/Cost price
Equal % profit & loss on the same selling price of two articles:
If two items are sold each at Rs X, one at a gain of p % and the other at a loss of p
%, then the two transactions have resulted in an overall loss of 2
p
%
100 , and the
absolute value of the loss is = Rs. 2
22
2.p .X
100 p
Equal % profit & loss on the same cost price of two articles:
If the cost price of two items is X, and one is sold at a profit of p % and the other at
a loss of p %, then the two transactions have resulted in no gain or no loss.
Trade Discount: To attract customers, it is a common practice to announce
discount on the marked price of an article.
Note: The discount is always taken as a % of the marked price, unless otherwise
specified.
E.g. Let the list price of an article be Rs. 450. A discount of 5% on its list price is
announced. Then, the new selling price = 450 x 95/100 = Rs 422.5.
Cash Discount: In addition to trade discount, the manufacturer may offer an
additional discount called the Cash Discount if the buyer makes full payment
within a certain specified time. Cash Discount is usually offered on the net price
(the price after subtracting discount from the marked price). Therefore, Cash
Price = Net Price - Cash Discount
Note: Cash discount is always calculated on net price, unless otherwise specified.
Wrong Weight: When a tradesman claims to sell at cost price, but uses a false
weight, then the percentage profit earned 100 Error
True weight Error
Successive Discounts: When a tradesman offers more than one discount to the
customer, then the total discount offered is calculated by applying the method of
decimals learned in the topic of percentage.
Example: A tradesman offers two successive discounts of 20 % and 10%. Calculate
the gross discount offered by the tradesman. 17 Ekoching
Your door to future
After a discount of 20%, we are left with 80% or 0.8. Further, after applying a
discount of 10%, we are left with 90% or 0.9. The total discount is calculated as:
1- (0.8 x 0.9) 0.28. Hence, there is a total discount of 28%.
When the SP of x articles is equal to CP of y articles, what is the profit percent
earned?
Profit percent 100 difference in x and y
X
7. Ratio, Mixture & Partnership
A. Ratio & Proportion
A Ratio is the relation between two quantities of the same kind. This relation
indicates how many times one quantity is equal to the other. In other words, ratio
is a number, which expresses one quantity as a fraction of the other.
Example: Ratio of 12 to 13 is 12/13 or 12:13.
The numbers forming the ratio are called terms. The numerator, i.e. "12", is known
as the antecedent and the denominator, i.e. "13", in this case, is known as the
consequent.
The ratio between two quantities a and b if expressed as a/b, is called fractional
form and, a: b is called linear form.
If two different ratios, a b and c d are expressed in different units, then the two are
compounded to obtain a combined ratio.
Compounding of a: b and c d yields a x c/b x d.
If a c e
,
b d f
then each of these ratios is equal to a c e
b d f
If ac
bd
, then bd
ac
(invertendo)
If ac
bd
, then ab
cd
(Alterendo)
If ac
bd
, then a b c d
bd
(componendo)
If ac
,
bd
then a b c d
bd
(Dividendo)
If ac
,
bd
then a b c d
a b c d
(Componendo dividend)
Continued Proportion: Four numbers a, b, c and d are said to be in proportion if a: b =
c : d. If on the other hand, a: b = b:cc:d, then the four numbers are said to be in
continued proportion.
Let us consider the ratios, a: b = b: c. Here b is called the mean proportional and is
equal to the square root of the product of a and c i.e. b²= a xc = b =ac
If a/b = b/c = c/d etc., then a, b, c, d are in geometric progression. Let a/b = b/c =
c/dk, then, c = dk; b = ck and a = bk
Since c = dk, b = dk x k = dk² and a = bk = dk² x k = dk³, implying that they are in
geometric progression.
If the three ratios, a: b, b: c, c: d are known, we can find a : d by the multiplying these
three ratios a/d = a/b x b/c x c/d
If a, b, c and d are four terms and the ratios a: b, b: c, c: d are known, then one can find
the ratio a: b :c:d.
18 Ekoching
Your door to future
discount of 10%, we are left with 90% or 0.9. The total discount is calculated as:
1- (0.8 x 0.9) 0.28. Hence, there is a total discount of 28%.
When the SP of x articles is equal to CP of y articles, what is the profit percent
earned?
Profit percent 100 difference in x and y
X
7. Ratio, Mixture & Partnership
A. Ratio & Proportion
A Ratio is the relation between two quantities of the same kind. This relation
indicates how many times one quantity is equal to the other. In other words, ratio
is a number, which expresses one quantity as a fraction of the other.
Example: Ratio of 12 to 13 is 12/13 or 12:13.
The numbers forming the ratio are called terms. The numerator, i.e. "12", is known
as the antecedent and the denominator, i.e. "13", in this case, is known as the
consequent.
The ratio between two quantities a and b if expressed as a/b, is called fractional
form and, a: b is called linear form.
If two different ratios, a b and c d are expressed in different units, then the two are
compounded to obtain a combined ratio.
Compounding of a: b and c d yields a x c/b x d.
If a c e
,
b d f
then each of these ratios is equal to a c e
b d f
If ac
bd
, then bd
ac
(invertendo)
If ac
bd
, then ab
cd
(Alterendo)
If ac
bd
, then a b c d
bd
(componendo)
If ac
,
bd
then a b c d
bd
(Dividendo)
If ac
,
bd
then a b c d
a b c d
(Componendo dividend)
Continued Proportion: Four numbers a, b, c and d are said to be in proportion if a: b =
c : d. If on the other hand, a: b = b:cc:d, then the four numbers are said to be in
continued proportion.
Let us consider the ratios, a: b = b: c. Here b is called the mean proportional and is
equal to the square root of the product of a and c i.e. b²= a xc = b =ac
If a/b = b/c = c/d etc., then a, b, c, d are in geometric progression. Let a/b = b/c =
c/dk, then, c = dk; b = ck and a = bk
Since c = dk, b = dk x k = dk² and a = bk = dk² x k = dk³, implying that they are in
geometric progression.
If the three ratios, a: b, b: c, c: d are known, we can find a : d by the multiplying these
three ratios a/d = a/b x b/c x c/d
If a, b, c and d are four terms and the ratios a: b, b: c, c: d are known, then one can find
the ratio a: b :c:d.
18 Ekoching
Your door to future
Variation – Direct, Inverse
(i) If a is directly proportional to b, then the ratio of a and b is constant.
(ii) if a is inversely proportional to b, then the product of a and b is constant.
(iii) If a b and b c, the a c.
(iv) If a b and a c, the a (b c).
(v) If a b and c d, then ac bd.
B. Alligation and Mixture
In Mixture problems, different substances are combined, and characteristics of the
resulting mixture have to be determined.
In solving mixture problems, we use the Alligation Rule (Alligation means
'linking'). The rule states, that "When different quantities of different ingredients
are mixed together to produce a mixture of a mean value, the ratio of their
quantities is inversely proportional to the differences in their cost from the mean
value."
One case in mixtures is, repeated
dilution of a mixture with one of the
ingredients, by removing, say n litres of
the mixture and replacing it with n
litres of one of the ingredients. Say
there are m litres of water initially. We
now remove n litres of the water and
replace it by n litres of wine. This
operation is done times. Then,
Quantity of water left in the vessel
= m(1-n/m)'
Where
m = Total quantity
n = Quantity drawn every time
t = No. of times
C. Partnership
Partnership is an association of two or more persons who invest money together
in order to carry out a certain business. Partnerships are of two types:
(i) Simple Partnership: When all partners invest in the business at the same time
i.e. their capital remains in the business for the same duration it is called simple
partnership. In this kind of partnership, the profit is simply distributed amongst
the partners, in the ratio of their respective invested capital.
(ii) Compound Partnership: When capital of the partners is invested in the
business for different time periods, the partnership is known as compound
partnership. In this, the profit sharing ratio is calculated by multiplying the capital
invested with the unit of time (mostly months).
The sharing of profit and loss can be better understood with the help of the
following illustrations:
Rule 1: In a simple partnership, the loss or profit is distributed amongst the
partners in the ratio of their respective investments. 19 Ekoching
Your door to future
(i) If a is directly proportional to b, then the ratio of a and b is constant.
(ii) if a is inversely proportional to b, then the product of a and b is constant.
(iii) If a b and b c, the a c.
(iv) If a b and a c, the a (b c).
(v) If a b and c d, then ac bd.
B. Alligation and Mixture
In Mixture problems, different substances are combined, and characteristics of the
resulting mixture have to be determined.
In solving mixture problems, we use the Alligation Rule (Alligation means
'linking'). The rule states, that "When different quantities of different ingredients
are mixed together to produce a mixture of a mean value, the ratio of their
quantities is inversely proportional to the differences in their cost from the mean
value."
One case in mixtures is, repeated
dilution of a mixture with one of the
ingredients, by removing, say n litres of
the mixture and replacing it with n
litres of one of the ingredients. Say
there are m litres of water initially. We
now remove n litres of the water and
replace it by n litres of wine. This
operation is done times. Then,
Quantity of water left in the vessel
= m(1-n/m)'
Where
m = Total quantity
n = Quantity drawn every time
t = No. of times
C. Partnership
Partnership is an association of two or more persons who invest money together
in order to carry out a certain business. Partnerships are of two types:
(i) Simple Partnership: When all partners invest in the business at the same time
i.e. their capital remains in the business for the same duration it is called simple
partnership. In this kind of partnership, the profit is simply distributed amongst
the partners, in the ratio of their respective invested capital.
(ii) Compound Partnership: When capital of the partners is invested in the
business for different time periods, the partnership is known as compound
partnership. In this, the profit sharing ratio is calculated by multiplying the capital
invested with the unit of time (mostly months).
The sharing of profit and loss can be better understood with the help of the
following illustrations:
Rule 1: In a simple partnership, the loss or profit is distributed amongst the
partners in the ratio of their respective investments. 19 Ekoching
Your door to future
Example: Say, P and Q invested Rs. a and b for one year in a business. Then, the
share of profit or loss will be,
P's profit/ loss: Q's profit/ loss = a: b
Rule 2: In a compound partnership, the profit or loss ratio is calculated as capital
multiplied by the duration of investment.
Example: P's profit/loss: Q's profit/loss = 12a t :b t
Where, t₁ = P's duration of investment and, t₂ = Q's duration of investment
8. Time and Work
If a person can do a certain task in t hours, then in 1 hour he would do 1/t
portion of the task. A does a particular job in 'a' hours and B does the same
job in 'b' hours, together they will take ab
ab hours.
A does a particular job in 'a' hours more than A and B combined whereas B
does the same job in 'b' hours more than A and B combined, then together
they will take ab hours to finish the job.
A does a particular job in 'a' hours, B does the same job in 'b' hours and C
does the same job in 'c' hours, then together they will take abc
ab bc ca
hours.
If A does a particular job in 'a' hours and A & B together do the job in 't'
hours, the B alone will take at
at hours.
If A does a particular job in 'a' hours, B does the same job in 'b' hours and
A, B and C together do the job in 't' hours, then
C alone can do it in abt
ab at bt hours.
A and C together can do it in bt
bt hours.
B and C together can do it in at
at hours
If the objective is to fill the tank, then the Inlet pipes do positive work
whereas the Outlet pipes do negative work. If the objective is to empty the
tank, then the Outlet pipes do positive work whereas the Inlet Pipes do
negative work.
There is one important expression that helps you solve many time and
work questions easily. Remember this expression MET W , which means 1 1 1 1 2 2 2 2M E T / W M E T / W
, where
M-no. of men
E-Efficiency of each man
T-amount of time they worked
W-amount of work done
9. Time, Speed & Distance
A. Basics of Time, Speed & Distance
The most important relationship between these three quantities, and possibly the
only one which needs to be known is, 20 Ekoching
Your door to future
share of profit or loss will be,
P's profit/ loss: Q's profit/ loss = a: b
Rule 2: In a compound partnership, the profit or loss ratio is calculated as capital
multiplied by the duration of investment.
Example: P's profit/loss: Q's profit/loss = 12a t :b t
Where, t₁ = P's duration of investment and, t₂ = Q's duration of investment
8. Time and Work
If a person can do a certain task in t hours, then in 1 hour he would do 1/t
portion of the task. A does a particular job in 'a' hours and B does the same
job in 'b' hours, together they will take ab
ab hours.
A does a particular job in 'a' hours more than A and B combined whereas B
does the same job in 'b' hours more than A and B combined, then together
they will take ab hours to finish the job.
A does a particular job in 'a' hours, B does the same job in 'b' hours and C
does the same job in 'c' hours, then together they will take abc
ab bc ca
hours.
If A does a particular job in 'a' hours and A & B together do the job in 't'
hours, the B alone will take at
at hours.
If A does a particular job in 'a' hours, B does the same job in 'b' hours and
A, B and C together do the job in 't' hours, then
C alone can do it in abt
ab at bt hours.
A and C together can do it in bt
bt hours.
B and C together can do it in at
at hours
If the objective is to fill the tank, then the Inlet pipes do positive work
whereas the Outlet pipes do negative work. If the objective is to empty the
tank, then the Outlet pipes do positive work whereas the Inlet Pipes do
negative work.
There is one important expression that helps you solve many time and
work questions easily. Remember this expression MET W , which means 1 1 1 1 2 2 2 2M E T / W M E T / W
, where
M-no. of men
E-Efficiency of each man
T-amount of time they worked
W-amount of work done
9. Time, Speed & Distance
A. Basics of Time, Speed & Distance
The most important relationship between these three quantities, and possibly the
only one which needs to be known is, 20 Ekoching
Your door to future
Distance = Speed Time
Speed Distance travelled/Time
Time = Distance travelled/Speed
• Average speed, if equal distances are covered at a km/hr and b km/hr is
2ab/a+b
• If two bodies are moving in the same direction at a speed of a and b
respectively, then their relative speed is the difference of the two speeds.
• If two bodies are moving in the opposite directions at a speed of a and b
respectively, then their relative speed is a + b.
• Two objects A and B moving along a circular path in the same direction, having
started simultaneously and from the same point traveling at speeds of a and b,
will meet again when the faster object has gained one full circle over the slower
object, i.e. when the relative speed a-b) completes one full round. The two
objects will again meet at the starting point at a time, which is the LCM of the
time taken for each of the objects individually to complete one round.
• If the length of a train is L meters and the speed of the train is S m/s, then the
time taken by the train to pass a stationary man/pole is L/S sec.
• If the length of the train is L, and its speed is S m/s and the length of a platform
(stationary object of comparable length) is L2, then the time taken by the train
to cross the platform is (L, + L₂)/S sec.
• If the lengths of 2 trains are L, (faster) and L2 (slower) m, and their speeds are
S, and S₂ m/s resp., then the time taken by the faster train to overtake the
slower train is L,+L2/ S,+S₂ sec, and the time taken for the trains to cross each
other is L,+L2/S,+S₂ sec.
B. Boats and Stream:
If the speed of the boat in still water is say B kmph and if the speed at which the
stream is flowing is W kmph,
(i) When the boat is traveling with the stream the speed of the boat
Down stream speed = (B W) kmph
(ii) When the boat is traveling against the stream the speed of the boat
Upstream speed(B W) kmph
(iii) If the upstream speed is denoted as U and downstream speed is denoted as
D then B (D U)/2,W (D U)/2
(ii) Total time taken by the boat that is travelling at speed B for distance uD
upstream and distance dD downstream in a river flowing at speed W is
U D u dT T T (D / (B W)) (D / B W))
Important Distance and Time Conversions:
1 km = 1000 meter 1 meter = 100 cm
1 hour = 60 min 1 min = 60 sec
1 hour = 3600 sec 1 km/hr = (1 1000) 5
m / sec.
(1 3600) 18
C. Races
If A beats B by x metres or s seconds, then the speed of B is x/s metres/sec. 21 Ekoching
Your door to future
Speed Distance travelled/Time
Time = Distance travelled/Speed
• Average speed, if equal distances are covered at a km/hr and b km/hr is
2ab/a+b
• If two bodies are moving in the same direction at a speed of a and b
respectively, then their relative speed is the difference of the two speeds.
• If two bodies are moving in the opposite directions at a speed of a and b
respectively, then their relative speed is a + b.
• Two objects A and B moving along a circular path in the same direction, having
started simultaneously and from the same point traveling at speeds of a and b,
will meet again when the faster object has gained one full circle over the slower
object, i.e. when the relative speed a-b) completes one full round. The two
objects will again meet at the starting point at a time, which is the LCM of the
time taken for each of the objects individually to complete one round.
• If the length of a train is L meters and the speed of the train is S m/s, then the
time taken by the train to pass a stationary man/pole is L/S sec.
• If the length of the train is L, and its speed is S m/s and the length of a platform
(stationary object of comparable length) is L2, then the time taken by the train
to cross the platform is (L, + L₂)/S sec.
• If the lengths of 2 trains are L, (faster) and L2 (slower) m, and their speeds are
S, and S₂ m/s resp., then the time taken by the faster train to overtake the
slower train is L,+L2/ S,+S₂ sec, and the time taken for the trains to cross each
other is L,+L2/S,+S₂ sec.
B. Boats and Stream:
If the speed of the boat in still water is say B kmph and if the speed at which the
stream is flowing is W kmph,
(i) When the boat is traveling with the stream the speed of the boat
Down stream speed = (B W) kmph
(ii) When the boat is traveling against the stream the speed of the boat
Upstream speed(B W) kmph
(iii) If the upstream speed is denoted as U and downstream speed is denoted as
D then B (D U)/2,W (D U)/2
(ii) Total time taken by the boat that is travelling at speed B for distance uD
upstream and distance dD downstream in a river flowing at speed W is
U D u dT T T (D / (B W)) (D / B W))
Important Distance and Time Conversions:
1 km = 1000 meter 1 meter = 100 cm
1 hour = 60 min 1 min = 60 sec
1 hour = 3600 sec 1 km/hr = (1 1000) 5
m / sec.
(1 3600) 18
C. Races
If A beats B by x metres or s seconds, then the speed of B is x/s metres/sec. 21 Ekoching
Your door to future
If the length of a circular track is L m, and if A and B take x and y sec. respectively,
to complete one round, then both of them will meet at the starting point after
LCM (x, y) sec.
If the length of a circular track is L m, and if the speeds of A and B are x m/sec.
and y m/sec respectively, then the time after which both of them will meet at a
point other than the starting point is L/x-y sec, if they are running in the same
direction and L/x+y, if running in the opposite direction.
10. Geometry & Mensuration
A. Rectangular Solids and Cylinders
Cuboid: A cuboid is a three-dimensional figure formed by six rectangular
surfaces, as shown below. Each rectangular surface is a face. Each solid line
segment is an edge, and each point at which the edges meet is a vertex. A
rectangular solid has six faces, twelve edges, and eight vertices. Edges mean
sides and vertices mean corners. Opposite faces are parallel rectangles that have
the same dimensions.
The surface area of a rectangular solid is equal to the sum of the areas of all the
faces. The volume is equal to (length) x (width) x (height); in other words, (area
of base) x (height).
Body diagonal of a cuboid Length of the longest rod that can be kept inside a
rectangular room is = 2 2 2
L B H
Cube: A rectangular solid in which all edges are of equal length is a cube. In a
cube, just like cuboid, there are six faces, eight vertices & twelve edges.
Volume = a³.
Surface Area = 6a², where a is the side of a cube.
Body Diagonal Length of the longest rod inside a cubical room = a3
Right Prism:
A prism is a solid, whose vertical faces are rectangular and whose bases are
parallel polygons of equal area.
A prism is said to be triangular prism, pentagonal prism, hexagonal prism,
octagonal prism according to the number of sides of the polygon that form the
base.
In a prism with a base of n sides, number of vertices = 2n, number of faces
= n + 2.
Curved Surface area of vertical faces of a prism = perimeter of base height.
Total surface area of a prism = perimeter of base height + 2 area of base
Volume of a prism = area of base height 22 Ekoching
Your door to future
to complete one round, then both of them will meet at the starting point after
LCM (x, y) sec.
If the length of a circular track is L m, and if the speeds of A and B are x m/sec.
and y m/sec respectively, then the time after which both of them will meet at a
point other than the starting point is L/x-y sec, if they are running in the same
direction and L/x+y, if running in the opposite direction.
10. Geometry & Mensuration
A. Rectangular Solids and Cylinders
Cuboid: A cuboid is a three-dimensional figure formed by six rectangular
surfaces, as shown below. Each rectangular surface is a face. Each solid line
segment is an edge, and each point at which the edges meet is a vertex. A
rectangular solid has six faces, twelve edges, and eight vertices. Edges mean
sides and vertices mean corners. Opposite faces are parallel rectangles that have
the same dimensions.
The surface area of a rectangular solid is equal to the sum of the areas of all the
faces. The volume is equal to (length) x (width) x (height); in other words, (area
of base) x (height).
Body diagonal of a cuboid Length of the longest rod that can be kept inside a
rectangular room is = 2 2 2
L B H
Cube: A rectangular solid in which all edges are of equal length is a cube. In a
cube, just like cuboid, there are six faces, eight vertices & twelve edges.
Volume = a³.
Surface Area = 6a², where a is the side of a cube.
Body Diagonal Length of the longest rod inside a cubical room = a3
Right Prism:
A prism is a solid, whose vertical faces are rectangular and whose bases are
parallel polygons of equal area.
A prism is said to be triangular prism, pentagonal prism, hexagonal prism,
octagonal prism according to the number of sides of the polygon that form the
base.
In a prism with a base of n sides, number of vertices = 2n, number of faces
= n + 2.
Curved Surface area of vertical faces of a prism = perimeter of base height.
Total surface area of a prism = perimeter of base height + 2 area of base
Volume of a prism = area of base height 22 Ekoching
Your door to future
Cylinder: Total Surface area of a right circular cylinder with a base of radius 'r'
and height 'h' is equal to 2(x²) + 2xrh (the sum of the areas of the two bases plus
the area of the curved surface).
The volume of a cylinder is equal to 2
rh , that is (area of base) (height).
Cone: A cone is having one circle on one of its ending & rest is the curved circle
part with a corner on the other end.
Volume=1/3 rh. Surface Area (curved)= r I, where I slant height.
As per the Pythagoras theorem, l²=r
2
+ h².
Surface Area (total) = 2
rl r .
Frustum of a cone: A frustum is the lower part of a cone, containing the base,
when it is cut by a plane parallel to the base of the cone.
Slant height, 22
L h (R r)
Curved Surface area of cone =(R r)L.
Total surface area of frustum = Base area + Area of upper circle + Area of lateral
surface = (R² + r² + RL + rL).
Volume of frustum = Sphere: The set of all points in space, which are at a fixed
distance from a fixed point, is called a sphere. The fixed point is the centre of the
sphere and the fixed distance is the radius of the sphere. Volume = 34
r
3
Surface
Area (curved and total) = 2
4r .
Hemisphere: A sphere cut by a plane passing through its centre forms two
hemispheres. The upper surface of a hemisphere is a circular region. Volume =
2/3πr. Surface Area (curved) =2
2r .
Surface Area (Total) = 2 2 2
2 r r 3 r
Spherical shell: If R and r are the outer and inner radius of a hollow sphere, then
volume of material in a spherical shell = 334
(R r ).
3
Pyramid:
A pyramid is a solid, whose lateral faces are triangular with a common vertex
and whose base is a polygon. A pyramid is said to be tetrahedron (triangular
base), square pyramid, hexagonal pyramid etc, according to the number of sides
of the polygon that form the base.
In a pyramid with a base of n sides, number of vertices = n + 1. Number of faces
including the base = n + 1.
Surface area of lateral faces
= 1
2
perimeter of base x slant height
Total surface area of pyramid
= Base area + 1
2
perimeter of base × slant height
Volume of pyramid = 1
3
Base area height. A cone is also a pyramid.
B. Lines and Angles
Some important points:
(i) There is one and only one line passing through two distinct points.
(ii) Three or more points are said to be collinear if they lie on a line, otherwise
they are said to be non collinear. 23 Ekoching
Your door to future
and height 'h' is equal to 2(x²) + 2xrh (the sum of the areas of the two bases plus
the area of the curved surface).
The volume of a cylinder is equal to 2
rh , that is (area of base) (height).
Cone: A cone is having one circle on one of its ending & rest is the curved circle
part with a corner on the other end.
Volume=1/3 rh. Surface Area (curved)= r I, where I slant height.
As per the Pythagoras theorem, l²=r
2
+ h².
Surface Area (total) = 2
rl r .
Frustum of a cone: A frustum is the lower part of a cone, containing the base,
when it is cut by a plane parallel to the base of the cone.
Slant height, 22
L h (R r)
Curved Surface area of cone =(R r)L.
Total surface area of frustum = Base area + Area of upper circle + Area of lateral
surface = (R² + r² + RL + rL).
Volume of frustum = Sphere: The set of all points in space, which are at a fixed
distance from a fixed point, is called a sphere. The fixed point is the centre of the
sphere and the fixed distance is the radius of the sphere. Volume = 34
r
3
Surface
Area (curved and total) = 2
4r .
Hemisphere: A sphere cut by a plane passing through its centre forms two
hemispheres. The upper surface of a hemisphere is a circular region. Volume =
2/3πr. Surface Area (curved) =2
2r .
Surface Area (Total) = 2 2 2
2 r r 3 r
Spherical shell: If R and r are the outer and inner radius of a hollow sphere, then
volume of material in a spherical shell = 334
(R r ).
3
Pyramid:
A pyramid is a solid, whose lateral faces are triangular with a common vertex
and whose base is a polygon. A pyramid is said to be tetrahedron (triangular
base), square pyramid, hexagonal pyramid etc, according to the number of sides
of the polygon that form the base.
In a pyramid with a base of n sides, number of vertices = n + 1. Number of faces
including the base = n + 1.
Surface area of lateral faces
= 1
2
perimeter of base x slant height
Total surface area of pyramid
= Base area + 1
2
perimeter of base × slant height
Volume of pyramid = 1
3
Base area height. A cone is also a pyramid.
B. Lines and Angles
Some important points:
(i) There is one and only one line passing through two distinct points.
(ii) Three or more points are said to be collinear if they lie on a line, otherwise
they are said to be non collinear. 23 Ekoching
Your door to future
(iii) Two or more lines are said to be coplanar if they lie in the same plane,
otherwise they are said to be non-coplanar.
(iv) A line, which is perpendicular to a line segment i.e., intersects at 90° and
passes through the midpoint of the segment is called he perpendicular
bisector of the segment.
(v) Every point on the perpendicular bisector of a segment is equidistant from
the two endpoints of the segment.
Conversely, if any point is equidistant from the two endpoints of the
segment, then it must lie on the perpendicular bisector of the segment.
If PO is the perpendicular bisector of segment AB, then, AP = PB.
Also, if AP = PB, then P lies on the perpendicular bisector of segment AB.
(vi) The ratio of intercepts made by three parallel
lines on a transversal is equal to the ratio of
the corresponding intercepts made on any
other transversal by the same parallel lines.
Angles:
When two rays have the same starting or end
points, they form an angle and the common end
point is called vertex.
Angle is also defined as the measure of rotation
of a ray. For the purpose of Trigonometry, the
measure of rotation is termed positive if it is in
the anticlockwise direction.
In the figure, ray PQ and QR from angle PQR
Types of Angles:
(i) Adjacent Angles:
POQ and QOR are called adjacent angles, because they have a
common side and their interiors are disjoint.
(ii) Linear Pair:
POR and ROQ are said to form a linear pair because they have a
common side and other two sides are opposite rays
POR+ ROQ=180° 24 Ekoching
Your door to future
otherwise they are said to be non-coplanar.
(iv) A line, which is perpendicular to a line segment i.e., intersects at 90° and
passes through the midpoint of the segment is called he perpendicular
bisector of the segment.
(v) Every point on the perpendicular bisector of a segment is equidistant from
the two endpoints of the segment.
Conversely, if any point is equidistant from the two endpoints of the
segment, then it must lie on the perpendicular bisector of the segment.
If PO is the perpendicular bisector of segment AB, then, AP = PB.
Also, if AP = PB, then P lies on the perpendicular bisector of segment AB.
(vi) The ratio of intercepts made by three parallel
lines on a transversal is equal to the ratio of
the corresponding intercepts made on any
other transversal by the same parallel lines.
Angles:
When two rays have the same starting or end
points, they form an angle and the common end
point is called vertex.
Angle is also defined as the measure of rotation
of a ray. For the purpose of Trigonometry, the
measure of rotation is termed positive if it is in
the anticlockwise direction.
In the figure, ray PQ and QR from angle PQR
Types of Angles:
(i) Adjacent Angles:
POQ and QOR are called adjacent angles, because they have a
common side and their interiors are disjoint.
(ii) Linear Pair:
POR and ROQ are said to form a linear pair because they have a
common side and other two sides are opposite rays
POR+ ROQ=180° 24 Ekoching
Your door to future
POR and POQ form a linear pair
(iii) An angle greater than 180°, but less than 360° is called a reflex angle.
(iv) Two angles whose sum is 90° are called complementary angles.
(v) Two angles having a sum of 180° are called supplementary angles.
(vi) When two lines intersect, two pairs of vertically opposite angles are equal.
The sum of 2 adjacent angles is 180°.
As given in the above diagram A = C &
B = D.
Secondly A + B =180° & C + D = 180°.
Two lines are parallel to each other if
• They are parallel to a 3
rd
line.
• They are opposite sides of a rectangle/ square/ rhombus/
parallelogram. If they are perpendicular to a 3
rd
line.
• If one of them is a side of the triangle & other joins the midpoints of
the remaining two sides.
• If one of them is a side of a triangle & other divides other 2 sides
proportionately.
Two lines are perpendicular to each other if
They are arms of a right-angle triangle.
If the adjacent angles formed by them are equal and supplementary.
They are adjacent sides of a rectangle or a square.
If they are diagonals of a rhombus.
If one of them is a tangent & other is radius of the circle through the
point of contact.
If the sum of their squares is equal to the square of line joining their
ends.
Two angles are said to be equal if
They are vertically opposite angles.
Their arms are parallel to each other.
They are the corresponding angles of two congruent triangles.
They are the opposite angles of a parallelogram.
They are the angles of an equilateral triangle.
They are the angles of a regular polygon.
They are in same segment of a circle.
One of them lies between a tangent & a chord thorough the point of
contact & other is in the alternate segment, in a circle.
Two sides are equal to each other if
They are corresponding sides of two congruent triangles.
They are sides of an equilateral triangle.
They are opposite sides of a parallelogram.
They are the sides of a regular polygon.
They are radii of the same circle.
They are chords equidistant from centre of circle. 25 Ekoching
Your door to future
(iii) An angle greater than 180°, but less than 360° is called a reflex angle.
(iv) Two angles whose sum is 90° are called complementary angles.
(v) Two angles having a sum of 180° are called supplementary angles.
(vi) When two lines intersect, two pairs of vertically opposite angles are equal.
The sum of 2 adjacent angles is 180°.
As given in the above diagram A = C &
B = D.
Secondly A + B =180° & C + D = 180°.
Two lines are parallel to each other if
• They are parallel to a 3
rd
line.
• They are opposite sides of a rectangle/ square/ rhombus/
parallelogram. If they are perpendicular to a 3
rd
line.
• If one of them is a side of the triangle & other joins the midpoints of
the remaining two sides.
• If one of them is a side of a triangle & other divides other 2 sides
proportionately.
Two lines are perpendicular to each other if
They are arms of a right-angle triangle.
If the adjacent angles formed by them are equal and supplementary.
They are adjacent sides of a rectangle or a square.
If they are diagonals of a rhombus.
If one of them is a tangent & other is radius of the circle through the
point of contact.
If the sum of their squares is equal to the square of line joining their
ends.
Two angles are said to be equal if
They are vertically opposite angles.
Their arms are parallel to each other.
They are the corresponding angles of two congruent triangles.
They are the opposite angles of a parallelogram.
They are the angles of an equilateral triangle.
They are the angles of a regular polygon.
They are in same segment of a circle.
One of them lies between a tangent & a chord thorough the point of
contact & other is in the alternate segment, in a circle.
Two sides are equal to each other if
They are corresponding sides of two congruent triangles.
They are sides of an equilateral triangle.
They are opposite sides of a parallelogram.
They are the sides of a regular polygon.
They are radii of the same circle.
They are chords equidistant from centre of circle. 25 Ekoching
Your door to future
They are tangents to a circle from an external point.
C. Triangles
Types of Triangles
With regard to their sides, triangles are of three types:
(i) Scalene Triangle: A triangle in which none of the three sides is equal is
called a scalene triangle.
(ii) Isosceles Triangle: A triangle in which at least two sides are
equal is called an isosceles triangle. In an isosceles triangle,
the angles opposite to the congruent sides are congruent.
Conversely, if two angles of a triangle are congruent, then
the sides opposite to them are congruent.
In ABC,AB AC, ABC ACB
(iii) Equilateral Triangle: A triangle in which all the three
sides are equal is called an equilateral triangle. In an
equilateral triangle, all the angles are congruent and
equal to 60°.
In A ABC, AB = BC = AC.
ZABC = BCA = CAB = 60°
With regard to their angles, triangles are of five types:
(i) Acute triangle: If all the three angles of a triangle are acute i.e., less than
90°, then the triangle is an acute-angled triangle.
(ii) Obtuse triangle: If any one angle of a triangle is obtuse i.e., greater than 90°,
then the triangle is an obtuse-angled triangle. The other two angles of the
obtuse triangle will be acute.
(iii) Right Triangle: A triangle that has a right angle is a right triangle. In a right
triangle, the side opposite the right angle is the hypotenuse, and the other
two sides are the legs. An important theorem concerning right triangles is
the Pythagorean theorem, which states: In a right triangle, the square of the
length of the hypotenuse is equal to the sum of the squares of the lengths
of the legs.
There are some standard Pythagorean triplets, which are repeatedly used
in the questions. It is better to remember these triplets by heart.
▲ 3,4,5 ▲ 5, 12, 13 ▲ 7, 24, 25 ▲ 8, 15, 17
▲ 9, 40, 41 ▲ 11, 60, 61 ▲ 12, 35, 37 ▲ 16, 63, 65
▲ 20, 21, 29 ▲ 28, 45, 53.
Any multiple of these triplets will also be a triplet i.e. when we say 3, 4, 5 is
a triplet, if we multiply all the numbers by 2, it will also be a triplet i.e. 6, 8,
10 will also be a triplet.
(iv) 45°- 45°-90° Triangle: If the angles of a triangle are 45°, 45° and 90°, then
the perpendicular sides are 1
2 times the hypotenuse. In a 45°- 45°-90°
triangle, the lengths of the sides are in the ratio 1:1: √2. For example, in
AJKL, ifJKL , then JK = 2, then JK =2 and KL = 2 . 26 Ekoching
Your door to future
C. Triangles
Types of Triangles
With regard to their sides, triangles are of three types:
(i) Scalene Triangle: A triangle in which none of the three sides is equal is
called a scalene triangle.
(ii) Isosceles Triangle: A triangle in which at least two sides are
equal is called an isosceles triangle. In an isosceles triangle,
the angles opposite to the congruent sides are congruent.
Conversely, if two angles of a triangle are congruent, then
the sides opposite to them are congruent.
In ABC,AB AC, ABC ACB
(iii) Equilateral Triangle: A triangle in which all the three
sides are equal is called an equilateral triangle. In an
equilateral triangle, all the angles are congruent and
equal to 60°.
In A ABC, AB = BC = AC.
ZABC = BCA = CAB = 60°
With regard to their angles, triangles are of five types:
(i) Acute triangle: If all the three angles of a triangle are acute i.e., less than
90°, then the triangle is an acute-angled triangle.
(ii) Obtuse triangle: If any one angle of a triangle is obtuse i.e., greater than 90°,
then the triangle is an obtuse-angled triangle. The other two angles of the
obtuse triangle will be acute.
(iii) Right Triangle: A triangle that has a right angle is a right triangle. In a right
triangle, the side opposite the right angle is the hypotenuse, and the other
two sides are the legs. An important theorem concerning right triangles is
the Pythagorean theorem, which states: In a right triangle, the square of the
length of the hypotenuse is equal to the sum of the squares of the lengths
of the legs.
There are some standard Pythagorean triplets, which are repeatedly used
in the questions. It is better to remember these triplets by heart.
▲ 3,4,5 ▲ 5, 12, 13 ▲ 7, 24, 25 ▲ 8, 15, 17
▲ 9, 40, 41 ▲ 11, 60, 61 ▲ 12, 35, 37 ▲ 16, 63, 65
▲ 20, 21, 29 ▲ 28, 45, 53.
Any multiple of these triplets will also be a triplet i.e. when we say 3, 4, 5 is
a triplet, if we multiply all the numbers by 2, it will also be a triplet i.e. 6, 8,
10 will also be a triplet.
(iv) 45°- 45°-90° Triangle: If the angles of a triangle are 45°, 45° and 90°, then
the perpendicular sides are 1
2 times the hypotenuse. In a 45°- 45°-90°
triangle, the lengths of the sides are in the ratio 1:1: √2. For example, in
AJKL, ifJKL , then JK = 2, then JK =2 and KL = 2 . 26 Ekoching
Your door to future
(v) 30°- 60°-90° Triangle: In 30°- 60°-90° triangle, the lengths of the sides are
in the ratio 1: 3 :2 . For example, in a triangle XYZ, if XZ = 3, then XY = 33
and YZ = 6. In short, the following formulas can be applied to calculate
the two sides of a 30 60 90 triangle, when the third side is given.
Side opposite to 1
30
2
of hypotenuse.
Side opposite to 3
60
2
of hypotenuse.
(v) 30 30 120 Triangle: In 30 30 120 triangle, the lengths of the
sides are in the ratio 1:1: 3 . For example, in a triangle ABC, if AB = c = 3,
then BC =a= 33 and AC = b = 3. In short, the following formulas can be
applied to calculate the two sides of a 30 60 90 triangle, when the
third side is given.
Some important properties of triangles:
(i) In ABC, ABC + BAC + ACB = 180°
(ii) The sum of an interior angle and the adjacent exterior angle is 180°.
In figure, ABC + ABH = 180°
ABC + CBI = 180°
(iii) Two exterior angles having the same vertex are congruent.
In figure, CAB FAC
(iv) The measure of an exterior angle is equal to the sum of the measures of the
two interior angles (called remote interior angles) of the triangle, not adjacent
to it.
(v) The sum of any two sides of a triangle is always greater than the third side. 27 Ekoching
Your door to future
in the ratio 1: 3 :2 . For example, in a triangle XYZ, if XZ = 3, then XY = 33
and YZ = 6. In short, the following formulas can be applied to calculate
the two sides of a 30 60 90 triangle, when the third side is given.
Side opposite to 1
30
2
of hypotenuse.
Side opposite to 3
60
2
of hypotenuse.
(v) 30 30 120 Triangle: In 30 30 120 triangle, the lengths of the
sides are in the ratio 1:1: 3 . For example, in a triangle ABC, if AB = c = 3,
then BC =a= 33 and AC = b = 3. In short, the following formulas can be
applied to calculate the two sides of a 30 60 90 triangle, when the
third side is given.
Some important properties of triangles:
(i) In ABC, ABC + BAC + ACB = 180°
(ii) The sum of an interior angle and the adjacent exterior angle is 180°.
In figure, ABC + ABH = 180°
ABC + CBI = 180°
(iii) Two exterior angles having the same vertex are congruent.
In figure, CAB FAC
(iv) The measure of an exterior angle is equal to the sum of the measures of the
two interior angles (called remote interior angles) of the triangle, not adjacent
to it.
(v) The sum of any two sides of a triangle is always greater than the third side. 27 Ekoching
Your door to future
In ABC, AB + BC > AC, also AB + AC > BC and AC + BC > AB.
(vi) The difference of any two sides is always less than the third side.
Area of a triangle
Area of a triangle 1 abc 1
base height s(s a)(s b)(s c) r s absin(C)
2 4R 2
where, a, b and c are the sides of the triangle,
s = semi perimetera b c
,r
2
in-radius, R = circum-radius, C=interior angle between
the sides a and b.
Number of possible Triangles with Integer sides for a given perimeter.
If the perimeter p is even then, total triangles is [p 2]/ 48
.
If the perimeter p is odd then, total triangles is [p 3] 2]/ 48
Where [x] represents nearest integer function.
In-centre: Point of intersection of angles
bisectors of a triangle is known as
the in-centre of triangle. The circle
drawn from this point, which
touches all the three sides of the
triangle, is known as in-circle & its
radius is called as in-radius. The in-
radius is denoted by the letter 'r'
(i) If A(x₁, y₁), B(X2, y2) and C(Xs, Ys) are the co-ordinates of a triangle and a, b, c
are the lengths of sides BC, AC and AB respectively then co-ordinates of the in
centre are: 1 2 3 2 3ax bx cx ay1 by cy
,
a b c a b c
(ii) In centre is equidistant for all the three sides, in-circle can be drawn touching all
the three sides.
The radius of this 'circle' is termed as 'in-radius'
i.e. r = Area of the triangle
s Semiperimeter of the triangle
(iii) AB AE
(AngleBisector theorem)
BC EC
(iv) If I is the in – centre, then 1
BIC 90 A
2
Circumcentre: It is the point of intersection of
perpendicular side bisectors of
the triangle.
The circle drawn with this point as centre and
passing through the vertices is known as circumcircle and its radius is called as
circumradius. The circumradius is denoted by the letter 'R'. 28 Ekoching
Your door to future
(vi) The difference of any two sides is always less than the third side.
Area of a triangle
Area of a triangle 1 abc 1
base height s(s a)(s b)(s c) r s absin(C)
2 4R 2
where, a, b and c are the sides of the triangle,
s = semi perimetera b c
,r
2
in-radius, R = circum-radius, C=interior angle between
the sides a and b.
Number of possible Triangles with Integer sides for a given perimeter.
If the perimeter p is even then, total triangles is [p 2]/ 48
.
If the perimeter p is odd then, total triangles is [p 3] 2]/ 48
Where [x] represents nearest integer function.
In-centre: Point of intersection of angles
bisectors of a triangle is known as
the in-centre of triangle. The circle
drawn from this point, which
touches all the three sides of the
triangle, is known as in-circle & its
radius is called as in-radius. The in-
radius is denoted by the letter 'r'
(i) If A(x₁, y₁), B(X2, y2) and C(Xs, Ys) are the co-ordinates of a triangle and a, b, c
are the lengths of sides BC, AC and AB respectively then co-ordinates of the in
centre are: 1 2 3 2 3ax bx cx ay1 by cy
,
a b c a b c
(ii) In centre is equidistant for all the three sides, in-circle can be drawn touching all
the three sides.
The radius of this 'circle' is termed as 'in-radius'
i.e. r = Area of the triangle
s Semiperimeter of the triangle
(iii) AB AE
(AngleBisector theorem)
BC EC
(iv) If I is the in – centre, then 1
BIC 90 A
2
Circumcentre: It is the point of intersection of
perpendicular side bisectors of
the triangle.
The circle drawn with this point as centre and
passing through the vertices is known as circumcircle and its radius is called as
circumradius. The circumradius is denoted by the letter 'R'. 28 Ekoching
Your door to future
Circum radius abc
4
Product of three sides
R
4 Area of the triangle
ZBOC=2 / A
Centroid: The segment joining a vertex & midpoint of the opposite side is called
median of a triangle. There are three medians & they meet in a single point
called, centroid of the triangle. The centroid divides medians in the ratio of 2: 1.
The following formula is applied to calculate the length of the median. The sum
of the squares of two sides = 2[median² + (rd1
3
2 side)
2
]
(i) If 1 1 2 2 3A(x ,y );B(x ,y );C(x ,ys) are the co-ordinates of a triangle, then co-
ordinates of centroid G are
1 2 3 1 2 3x x x y y y
,
33
(ii) The median divides the triangle in two equal parts (not necessarily
congruent)
(iii) The centroid divides the median in the ratio 2:1 with the larger part
towards the vertex. So AG: GD = 2:1.
Orthocentre: The line drawn from any vertex, perpendicular to the opposite side
is called the altitude/height. The three altitudes meet in a single point called the
orthocentre. The angle made by any side at orthocentre is equal to (180° vertical
angle).
If A ABC, is an isosceles triangle with AB AC, then the angle bisector of BAC is
the perpendicular bisector of the base BC and is also the median to the base.
Area of an isosceles triangle =22
4a , where c is the unequal side and a is one of 29 Ekoching
Your door to future
4
Product of three sides
R
4 Area of the triangle
ZBOC=2 / A
Centroid: The segment joining a vertex & midpoint of the opposite side is called
median of a triangle. There are three medians & they meet in a single point
called, centroid of the triangle. The centroid divides medians in the ratio of 2: 1.
The following formula is applied to calculate the length of the median. The sum
of the squares of two sides = 2[median² + (rd1
3
2 side)
2
]
(i) If 1 1 2 2 3A(x ,y );B(x ,y );C(x ,ys) are the co-ordinates of a triangle, then co-
ordinates of centroid G are
1 2 3 1 2 3x x x y y y
,
33
(ii) The median divides the triangle in two equal parts (not necessarily
congruent)
(iii) The centroid divides the median in the ratio 2:1 with the larger part
towards the vertex. So AG: GD = 2:1.
Orthocentre: The line drawn from any vertex, perpendicular to the opposite side
is called the altitude/height. The three altitudes meet in a single point called the
orthocentre. The angle made by any side at orthocentre is equal to (180° vertical
angle).
If A ABC, is an isosceles triangle with AB AC, then the angle bisector of BAC is
the perpendicular bisector of the base BC and is also the median to the base.
Area of an isosceles triangle =22
4a , where c is the unequal side and a is one of 29 Ekoching
Your door to future
the equal sides.
The altitudes on the congruent sides are equal i.e., BE = CF.
For an equilateral triangle,
Height = 3
2
side;
area 23
(side) ,
4
inradius 1
height;
3
Circumradius 2
height,
3
perimeter = 3 sides
Also, the altitude, median, angle bisector, perpendicular bisector of each base is
the same and the ortho-centre, centroid, in-centre and circum-centre is the
same.
Congruency of triangles: If the sides and angles of one triangle are equal to the
corresponding sides and angles of the other triangle, then the two triangles are
said to be congruent.
Two triangles are congruent if
Two sides & the included angle of a triangle are respectively equal to two sides
& included angle of other triangle (SAS).
2 angles & 1 side of a triangle are respectively equal to two angles & the
corresponding side of the other triangle (AAS).
Three sides of a triangle are respectively congruent to three sides of the other
triangle (SSS).
1 side & hypotenuse of a right-triangle are respectively congruent to 1 side &
hypotenuse of other rt. triangle (RHS).
Similarity of triangles:
Two triangles are similar if they alike in shape only. The corresponding
angles are congruent, but corresponding sides are only proportional. All
congruent triangles are similar but all similar triangles are not
necessarily congruent.
Two triangles are similar if
Three sides of a triangle are proportional to the three sides of the other
triangle (SSS).
Two angles of a triangle are respectively equal to the two angles of the
other triangle (AA).
Two sides of a triangle are proportional to two sides of the other triangle
& the included angles are equal (SAS).
Properties of similar triangles: 30 Ekoching
Your door to future
The altitudes on the congruent sides are equal i.e., BE = CF.
For an equilateral triangle,
Height = 3
2
side;
area 23
(side) ,
4
inradius 1
height;
3
Circumradius 2
height,
3
perimeter = 3 sides
Also, the altitude, median, angle bisector, perpendicular bisector of each base is
the same and the ortho-centre, centroid, in-centre and circum-centre is the
same.
Congruency of triangles: If the sides and angles of one triangle are equal to the
corresponding sides and angles of the other triangle, then the two triangles are
said to be congruent.
Two triangles are congruent if
Two sides & the included angle of a triangle are respectively equal to two sides
& included angle of other triangle (SAS).
2 angles & 1 side of a triangle are respectively equal to two angles & the
corresponding side of the other triangle (AAS).
Three sides of a triangle are respectively congruent to three sides of the other
triangle (SSS).
1 side & hypotenuse of a right-triangle are respectively congruent to 1 side &
hypotenuse of other rt. triangle (RHS).
Similarity of triangles:
Two triangles are similar if they alike in shape only. The corresponding
angles are congruent, but corresponding sides are only proportional. All
congruent triangles are similar but all similar triangles are not
necessarily congruent.
Two triangles are similar if
Three sides of a triangle are proportional to the three sides of the other
triangle (SSS).
Two angles of a triangle are respectively equal to the two angles of the
other triangle (AA).
Two sides of a triangle are proportional to two sides of the other triangle
& the included angles are equal (SAS).
Properties of similar triangles: 30 Ekoching
Your door to future
If two triangles are similar, ratios of sides = ratio of heights = ratio of
medians = ratio of angle bisectors = ratio of inradii = ratio of
circumradii.
Ratio of areas = b1h1/b₂h₂ = (s1)
2
/(s2)
2
, where b, & h, are the base &
height of first triangle and b₂ & h₂ are the base & height of second
triangle. S, & S₂ are the corresponding sides of first and second triangle
respectively.
Some important theorems:
(i) Basic Proportionality Theorem: If a line is drawn parallel
to one side of a triangle and intersects the other sides in
two distinct points, then the other sides are divided in
the same ratio by it. If DE is parallel to BC, then, AD AE
DB EC
(ii) The Angle Bisector Theorem: The angle bisector
divides the opposite side in ratio of the lengths of its
adjacent arms.
If AD is the angle bisector, then AB BD
AC DC
.
(iii) Midpoint Theorem: The segment joining the
midpoints of any two sides of a triangle is parallel to
the third side and is half of the third side.
If AD = DB, AE = EC, then DE is parallel to BC and 1
DE BC.
2
D. Circles
If r is the radius of the circle, then the circumference 2r ,
The area of a circle of radius r is = 2
r .
Congruent Circles: Circles with equal radii are called congruent circles.
Concentric Circles: Circles lying in the same plane with a common centre are
called concentric circles.
Some Important Properties of Circles
(i) The perpendicular from the centre of a circle to a chord of the circle bisects
the chord. 31 Ekoching
Your door to future
medians = ratio of angle bisectors = ratio of inradii = ratio of
circumradii.
Ratio of areas = b1h1/b₂h₂ = (s1)
2
/(s2)
2
, where b, & h, are the base &
height of first triangle and b₂ & h₂ are the base & height of second
triangle. S, & S₂ are the corresponding sides of first and second triangle
respectively.
Some important theorems:
(i) Basic Proportionality Theorem: If a line is drawn parallel
to one side of a triangle and intersects the other sides in
two distinct points, then the other sides are divided in
the same ratio by it. If DE is parallel to BC, then, AD AE
DB EC
(ii) The Angle Bisector Theorem: The angle bisector
divides the opposite side in ratio of the lengths of its
adjacent arms.
If AD is the angle bisector, then AB BD
AC DC
.
(iii) Midpoint Theorem: The segment joining the
midpoints of any two sides of a triangle is parallel to
the third side and is half of the third side.
If AD = DB, AE = EC, then DE is parallel to BC and 1
DE BC.
2
D. Circles
If r is the radius of the circle, then the circumference 2r ,
The area of a circle of radius r is = 2
r .
Congruent Circles: Circles with equal radii are called congruent circles.
Concentric Circles: Circles lying in the same plane with a common centre are
called concentric circles.
Some Important Properties of Circles
(i) The perpendicular from the centre of a circle to a chord of the circle bisects
the chord. 31 Ekoching
Your door to future
Conversely, the line joining the centre of the circle and the midpoint of a
chord is perpendicular to the chord.
(ii) Equal chords of a circle or congruent circles are equidistant from the
centre.
Conversely, two chords of a circle or congruent circles that are equidistant
from the centre are equal. Two chords PQ, RS intersect at a point then CP
CQ = CR CS
(iii) In a circle or congruent circles, equal chords subtend equal angles at the
centre.
Conversely, chords, which subtend equal angles at the centre of the same
or congruent circles, are equal.
(iv) If the two circles touch each other externally, distance between their
centres = sum of their radii.
32 Ekoching
Your door to future
chord is perpendicular to the chord.
(ii) Equal chords of a circle or congruent circles are equidistant from the
centre.
Conversely, two chords of a circle or congruent circles that are equidistant
from the centre are equal. Two chords PQ, RS intersect at a point then CP
CQ = CR CS
(iii) In a circle or congruent circles, equal chords subtend equal angles at the
centre.
Conversely, chords, which subtend equal angles at the centre of the same
or congruent circles, are equal.
(iv) If the two circles touch each other externally, distance between their
centres = sum of their radii.
32 Ekoching
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If the two circles touch each other internally, distance between their
centres = difference of their radii.
(v) The measure of an inscribed angle is half the measure of its intercepted arc.
(Inscribed angle theorem). 1
ACB AOB
2
(vi) Angles subtended is the same segment are equal
i.e. 12APB AP B.
(viii) Tangent is always perpendicular to the line joining the centre and the
point of tangency.
(ix) Two tangents from the same external point are equal in length. PA = PB
(x) If AB is any chord of a circle and PC is the tangent (both for a external
point P) than 2
PA PB PC
(xi) Length of direct common tangent =
22
12(distance between centres) (r r )
33 Ekoching
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centres = difference of their radii.
(v) The measure of an inscribed angle is half the measure of its intercepted arc.
(Inscribed angle theorem). 1
ACB AOB
2
(vi) Angles subtended is the same segment are equal
i.e. 12APB AP B.
(viii) Tangent is always perpendicular to the line joining the centre and the
point of tangency.
(ix) Two tangents from the same external point are equal in length. PA = PB
(x) If AB is any chord of a circle and PC is the tangent (both for a external
point P) than 2
PA PB PC
(xi) Length of direct common tangent =
22
12(distance between centres) (r r )
33 Ekoching
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(xii) Length of transverse common tangent =
22
12(distance between centres) (r r )
(xiii) Alternate Segment Theorem:
Angle between any chord (at the point of tangency) and the tangent is equal
to the angle subtended by the chord to any point on the other side of the
segment (altemate segment).
In the fig CBP2 = CAB = X° & P₁BA = ACB = Y⁰
Sectors of a Circle
The number of degrees of arc in a circle (or the number of degrees in a complete
revolution) is 360.
In the circle with center O above, the length of arc RS is x/360 of the circumference
of the circle; for example, if x = 60°, then arc RS has length 1/6 of the
circumference of the circle. We can remember the following formulas:
Length of arc RS = 2πr
2
x/360. the complete circle is having 360 degrees & any
part of that shall be equal to x/360.
34 Ekoching
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22
12(distance between centres) (r r )
(xiii) Alternate Segment Theorem:
Angle between any chord (at the point of tangency) and the tangent is equal
to the angle subtended by the chord to any point on the other side of the
segment (altemate segment).
In the fig CBP2 = CAB = X° & P₁BA = ACB = Y⁰
Sectors of a Circle
The number of degrees of arc in a circle (or the number of degrees in a complete
revolution) is 360.
In the circle with center O above, the length of arc RS is x/360 of the circumference
of the circle; for example, if x = 60°, then arc RS has length 1/6 of the
circumference of the circle. We can remember the following formulas:
Length of arc RS = 2πr
2
x/360. the complete circle is having 360 degrees & any
part of that shall be equal to x/360.
34 Ekoching
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Area of Sector 2
ORS r x/360 . the complete circle is having 360 degrees &
any part of that shall be equal to x/360.
Area of the segment of a circle (QSR) 2 sin
r
360 2
Perimeter of the segment 2 r 2rsin
360 2
E. Quadrilaterals & Polygons
Quadrilaterals
(i) of all the quadrilaterals of the same perimeter, the one with the maximum
area is the square.
(ii) The quadrilateral formed by joining the midpoints of the sides of any
quadrilateral is always a parallelogram (rhombus in case of a rectangle,
rectangle in case of a rhombus and square in case of a square).
(iii) The quadrilateral formed by the angle bisectors of the angles of a
parallelogram is a rectangle.
(iv) For a rhombus ABCD, if the diagonals are AC and BD, then AC² + BD² = 4 x
AB
2
.
(v) If a square is formed by joining the midpoints of a square, then the side of
the smaller square = side of the bigger square/2 .
(vi) If P is a point inside a rectangle ABCD, then AP
2
+ CP
2
= BP² + DP
2
(vii) The segment joining the midpoints of the non-parallel sides of a trapezium
is parallel to the two parallel sides and is half the sum of the parallel sides.
(viii) For a trapezium ABCD, if the diagonals are AC and BD, and AB and CD are
the parallel sides, then AC² + BD
2
= AD² + BC² + 2 X AB X BD.
(ix) If the length of the sides of a cyclic quadrilaterals area, b, c and d, then it's
area = (s a)(s b)(s c)(s d), where s is the semi-perimeter.
(x) The opposite angles of a cyclic quadrilateral are supplementary.
35 Ekoching
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ORS r x/360 . the complete circle is having 360 degrees &
any part of that shall be equal to x/360.
Area of the segment of a circle (QSR) 2 sin
r
360 2
Perimeter of the segment 2 r 2rsin
360 2
E. Quadrilaterals & Polygons
Quadrilaterals
(i) of all the quadrilaterals of the same perimeter, the one with the maximum
area is the square.
(ii) The quadrilateral formed by joining the midpoints of the sides of any
quadrilateral is always a parallelogram (rhombus in case of a rectangle,
rectangle in case of a rhombus and square in case of a square).
(iii) The quadrilateral formed by the angle bisectors of the angles of a
parallelogram is a rectangle.
(iv) For a rhombus ABCD, if the diagonals are AC and BD, then AC² + BD² = 4 x
AB
2
.
(v) If a square is formed by joining the midpoints of a square, then the side of
the smaller square = side of the bigger square/2 .
(vi) If P is a point inside a rectangle ABCD, then AP
2
+ CP
2
= BP² + DP
2
(vii) The segment joining the midpoints of the non-parallel sides of a trapezium
is parallel to the two parallel sides and is half the sum of the parallel sides.
(viii) For a trapezium ABCD, if the diagonals are AC and BD, and AB and CD are
the parallel sides, then AC² + BD
2
= AD² + BC² + 2 X AB X BD.
(ix) If the length of the sides of a cyclic quadrilaterals area, b, c and d, then it's
area = (s a)(s b)(s c)(s d), where s is the semi-perimeter.
(x) The opposite angles of a cyclic quadrilateral are supplementary.
35 Ekoching
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(i) Square = a²
(ii) Rectangle = a x b, where a & b are the length and breadth of the rectangle.
(iii) Parallelogram = b x h, where b is the base and h is the height of the
parallelogram.
(iv) For Rhombus =12
1
dd
2
, where d1 and d₂ are the diagonals of the
rhombus.
(v) For Trapezium with a and b parallel sides and height h, Area = 1
(a b)h
2
Polygons
(i) The sides an of regular in inscribed polygons, where R is the radius of the
circumscribed circle =na = 2R sin 180
n
(ii) Area of a polygon of perimeter P and radius of in-circle r = 1
pxr
2
(iii) The sum of the interior angles of a convex POLYGON, having n sides is 180°
(n-2).
(iv) The sum of the exterior angles of a convex polygon, taken one at each
vertex, is 360 .
(v) The measure of an exterior angle of a regular n-sided polygon is 360
n
.
(vi) The measure of the interior angle of a regular n-sided polygon is (n 2)180
n
.
(vii) The number of diagonals of in an n- sided polygon isn
2
n(n 3)
C n .
2
11. Co – ordinate Geometry
36 Ekoching
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(ii) Rectangle = a x b, where a & b are the length and breadth of the rectangle.
(iii) Parallelogram = b x h, where b is the base and h is the height of the
parallelogram.
(iv) For Rhombus =12
1
dd
2
, where d1 and d₂ are the diagonals of the
rhombus.
(v) For Trapezium with a and b parallel sides and height h, Area = 1
(a b)h
2
Polygons
(i) The sides an of regular in inscribed polygons, where R is the radius of the
circumscribed circle =na = 2R sin 180
n
(ii) Area of a polygon of perimeter P and radius of in-circle r = 1
pxr
2
(iii) The sum of the interior angles of a convex POLYGON, having n sides is 180°
(n-2).
(iv) The sum of the exterior angles of a convex polygon, taken one at each
vertex, is 360 .
(v) The measure of an exterior angle of a regular n-sided polygon is 360
n
.
(vi) The measure of the interior angle of a regular n-sided polygon is (n 2)180
n
.
(vii) The number of diagonals of in an n- sided polygon isn
2
n(n 3)
C n .
2
11. Co – ordinate Geometry
36 Ekoching
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(i) Distance PQ =
22
2 1 2 1x x y y
(ii) Slope of PQ = m = y2 – y1 / x2 – x1 = tanθ
(iii) Equation of PQ is y – y1/y1 – y2 = x – x1 / x1 – x2 or y = mx + c or xy
1
ab
Where,
a = x – intercept
b = y – intercept
(iv) The product of the slopes of two perpendicular lines is -1 and slopes of
parallel lines are equal.
(v) If point P(x, y) divides the segment AB, where
A = (x₁, y₁) and B = (x2, y2), internally in the ratio m: n, then,
2 1 2 1mx nx my ny
x andy
m n m n
.
(vi) A If point P(x, y) divides the segment AB, where
A = (x₁, y₁) and B = (x2, y2), externally in the ratio m: n, then,
2 1 2 1mx nx my ny
x and y
m n m n
(vii) If P(x,y) is the midpoint, then x = x1 + x2 /2 and y = y1 + y2/2.
(viii) If G (x, y) is the centroid of triangle ABC, A = (x1, y1), B = (x2, y2), C = (x3,
y3) then x = x1 + x2 + x3 /3 and y = y1 + y2 + y3 / 3.
(ix) If I (x,y) is the in – centre of triangle ABC.
1 1 2 2 3 3A (x ,y ),B (x ,y ),C (x ,y ), then x = ax1 + bx2 + cx3/ a + b + c and
y = ay1 + by2 + cy3 / a + b + c where a, b and c are the lengths of BC, AC
and AB respectively.
(x) The equation of a straight line is y = mx + c, where m is the slope and c is
the y-intercept (tan → = m, where → is the angle that the line makes with
the positive X-axis)
12. Set Theory
The set which does not contain any element is known as an empty set.
If every point of a set A belongs to B, then A is contained or included in B and is a
subset of B, while B is known as the superset of A. This is represented as A B or
BA. Two sets are identical if they contain exactly the same points, and is then
denoted as A = B.
Another way to represent this is: A B if and only if AB and B CA.
Two sets are said to be equivalent if they contain the same number of elements.
The set AB is the set of all those elements that belong to A, but not B and is called
the Difference set.
The set A A B is the set of all those elements that belong to either A or B, but not
both. It is called the symmetric difference set.
A B = (A B) - (A B).
A B (A-B) (B-A).
Empty set is a subset of every set.
Every set is a subset of itself.
The set of all subsets of a set is called the power set. It contains 2" elements, if the
original set contains n elements. 37 Ekoching
Your door to future
22
2 1 2 1x x y y
(ii) Slope of PQ = m = y2 – y1 / x2 – x1 = tanθ
(iii) Equation of PQ is y – y1/y1 – y2 = x – x1 / x1 – x2 or y = mx + c or xy
1
ab
Where,
a = x – intercept
b = y – intercept
(iv) The product of the slopes of two perpendicular lines is -1 and slopes of
parallel lines are equal.
(v) If point P(x, y) divides the segment AB, where
A = (x₁, y₁) and B = (x2, y2), internally in the ratio m: n, then,
2 1 2 1mx nx my ny
x andy
m n m n
.
(vi) A If point P(x, y) divides the segment AB, where
A = (x₁, y₁) and B = (x2, y2), externally in the ratio m: n, then,
2 1 2 1mx nx my ny
x and y
m n m n
(vii) If P(x,y) is the midpoint, then x = x1 + x2 /2 and y = y1 + y2/2.
(viii) If G (x, y) is the centroid of triangle ABC, A = (x1, y1), B = (x2, y2), C = (x3,
y3) then x = x1 + x2 + x3 /3 and y = y1 + y2 + y3 / 3.
(ix) If I (x,y) is the in – centre of triangle ABC.
1 1 2 2 3 3A (x ,y ),B (x ,y ),C (x ,y ), then x = ax1 + bx2 + cx3/ a + b + c and
y = ay1 + by2 + cy3 / a + b + c where a, b and c are the lengths of BC, AC
and AB respectively.
(x) The equation of a straight line is y = mx + c, where m is the slope and c is
the y-intercept (tan → = m, where → is the angle that the line makes with
the positive X-axis)
12. Set Theory
The set which does not contain any element is known as an empty set.
If every point of a set A belongs to B, then A is contained or included in B and is a
subset of B, while B is known as the superset of A. This is represented as A B or
BA. Two sets are identical if they contain exactly the same points, and is then
denoted as A = B.
Another way to represent this is: A B if and only if AB and B CA.
Two sets are said to be equivalent if they contain the same number of elements.
The set AB is the set of all those elements that belong to A, but not B and is called
the Difference set.
The set A A B is the set of all those elements that belong to either A or B, but not
both. It is called the symmetric difference set.
A B = (A B) - (A B).
A B (A-B) (B-A).
Empty set is a subset of every set.
Every set is a subset of itself.
The set of all subsets of a set is called the power set. It contains 2" elements, if the
original set contains n elements. 37 Ekoching
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In A B, the max value of the intersection An B is the min of n(A) and n(B).
In A B C, the maximum value of the intersection A B C is the minimum of
the intersections A B, B C and A C.
De Morgan's laws –
1. C C C
(A B) A B .
2. C C C
(A B) A B .
Operations with Venn Diagrams
The union A B of two sets A and B is the set of points, which belong to at
least one of them.
The intersection of sets A B of two sets A and B is the set of points which
belong to both of them
The Union of two sets, A B = A+B - A B
The Union of three sets A B C = A + B + C - (A B + B C + C A)
+ (A B C)
It is very important here to understand the meaning of certain terms.
• At least 1: means min. 1 i.e. 1 or more than 1.
• At least 2: means min. 2 i.e. 2 or more than 2.
At the most 2: means maximum 2 i.e. 2 or less than 2.
At the most 3 : means maximum 3 i.e. 3 or less than 3.
13. Logarithms
(i) Definition : a
x
= b can be represented in logarithmic form as loga b = x
(ii) log a = x means that 10
x
= a.
(iii) 10
loga
= a ( The basic logarithmic identity).
(iv) log(ab) = log a + log b, a > 0 , b > 0
(v) log a
b = log a – log b , a > 0, b > 0.
(vi) log a
n
= n (log a) (Logarithm of a power).
(vii) logx y =
m
m
log y
log x
(Change of base rule).
(viii) logxy = y
1
log x
(ix) logx1 = 0 (x 0,1).
(x) The natural numbers 1, 2, 3,... are respectively the logarithms of 10, 100,
1000, ... to the base 10.
(xi) The logarithm of "0" and negative numbers are not defined. 38 Ekoching
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In A B C, the maximum value of the intersection A B C is the minimum of
the intersections A B, B C and A C.
De Morgan's laws –
1. C C C
(A B) A B .
2. C C C
(A B) A B .
Operations with Venn Diagrams
The union A B of two sets A and B is the set of points, which belong to at
least one of them.
The intersection of sets A B of two sets A and B is the set of points which
belong to both of them
The Union of two sets, A B = A+B - A B
The Union of three sets A B C = A + B + C - (A B + B C + C A)
+ (A B C)
It is very important here to understand the meaning of certain terms.
• At least 1: means min. 1 i.e. 1 or more than 1.
• At least 2: means min. 2 i.e. 2 or more than 2.
At the most 2: means maximum 2 i.e. 2 or less than 2.
At the most 3 : means maximum 3 i.e. 3 or less than 3.
13. Logarithms
(i) Definition : a
x
= b can be represented in logarithmic form as loga b = x
(ii) log a = x means that 10
x
= a.
(iii) 10
loga
= a ( The basic logarithmic identity).
(iv) log(ab) = log a + log b, a > 0 , b > 0
(v) log a
b = log a – log b , a > 0, b > 0.
(vi) log a
n
= n (log a) (Logarithm of a power).
(vii) logx y =
m
m
log y
log x
(Change of base rule).
(viii) logxy = y
1
log x
(ix) logx1 = 0 (x 0,1).
(x) The natural numbers 1, 2, 3,... are respectively the logarithms of 10, 100,
1000, ... to the base 10.
(xi) The logarithm of "0" and negative numbers are not defined. 38 Ekoching
Your door to future
The logarithm of a number to the base "10" is known as common logarithm and
the logarithm of a number to the base "e" is known as natural logarithm.
Characteristic and Mantissa of Common Logarithms:
The integral part of the common logarithm of a number x > 0 is called the
Characteristic and the fractional part is called the mantissa.
e.g. the logarithm of 2 to the base 10 is 0.3010, where 0 is the characteristic and
3010 is the mantissa.
Any positive number "x" can be written in the form x = a10", where 1 < a < 10
and n is an integer. The number n is called the order of the number x. e.g. 30 can
be written as 3*10' and similarly 300 can be written 3*102. The same rule applies
to fractions as well where the value of n will be negative.
The characteristic of the logarithm of the given number "x" will be "n" and the
mantissa will be the logarithm of "a". Therefore, while log 2 = 0.3010, log 20 will
be 1.3010 as"n" in this case is "1".
Thus, the value of the characteristic of the logarithm of a number will help
determine the number of integral digits the number has characteristic + 1.
14. Permutation and Combination
Factorial, n = n (n – 1) (n – 2) …… 1
Eg. 5! = 5 4 3 2 1
Fundamental Principle of Counting
Multiplication: If there are two jobs such that one of them can be completed in m
ways, and when it has been completed in any one of these m ways, second job can
be completed in n ways, then the two jobs in succession can be completed in m x
n ways.
Addition: If there are two jobs such that they can be performed independently in
m and n ways respectively, then either of the two jobs can be performed in (m +
n) ways.
Note: The above principles of counting can be extended to any finite number of
jobs.
Permutation of n things taken r at a time, n
r
n!
P
(n r)!
= (Includes arrangement)
Combination of n things taken r at a time, n
r
n!
C
r!(n r)!
= (Includes only
selection) nn
rr
nn
r n r
P C r!
PC
The total number of combinations of n distinct things, taken none or some or all at
a time = 2
n
The total number of combinations of n things, r taken at a time, where p things
always occur = np
rpC
The total number of combinations of n things, r taken at a time, where p things will
never occur = np
rpC
39 Ekoching
Your door to future
the logarithm of a number to the base "e" is known as natural logarithm.
Characteristic and Mantissa of Common Logarithms:
The integral part of the common logarithm of a number x > 0 is called the
Characteristic and the fractional part is called the mantissa.
e.g. the logarithm of 2 to the base 10 is 0.3010, where 0 is the characteristic and
3010 is the mantissa.
Any positive number "x" can be written in the form x = a10", where 1 < a < 10
and n is an integer. The number n is called the order of the number x. e.g. 30 can
be written as 3*10' and similarly 300 can be written 3*102. The same rule applies
to fractions as well where the value of n will be negative.
The characteristic of the logarithm of the given number "x" will be "n" and the
mantissa will be the logarithm of "a". Therefore, while log 2 = 0.3010, log 20 will
be 1.3010 as"n" in this case is "1".
Thus, the value of the characteristic of the logarithm of a number will help
determine the number of integral digits the number has characteristic + 1.
14. Permutation and Combination
Factorial, n = n (n – 1) (n – 2) …… 1
Eg. 5! = 5 4 3 2 1
Fundamental Principle of Counting
Multiplication: If there are two jobs such that one of them can be completed in m
ways, and when it has been completed in any one of these m ways, second job can
be completed in n ways, then the two jobs in succession can be completed in m x
n ways.
Addition: If there are two jobs such that they can be performed independently in
m and n ways respectively, then either of the two jobs can be performed in (m +
n) ways.
Note: The above principles of counting can be extended to any finite number of
jobs.
Permutation of n things taken r at a time, n
r
n!
P
(n r)!
= (Includes arrangement)
Combination of n things taken r at a time, n
r
n!
C
r!(n r)!
= (Includes only
selection) nn
rr
nn
r n r
P C r!
PC
The total number of combinations of n distinct things, taken none or some or all at
a time = 2
n
The total number of combinations of n things, r taken at a time, where p things
always occur = np
rpC
The total number of combinations of n things, r taken at a time, where p things will
never occur = np
rpC
39 Ekoching
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The number of ways of dividing n things into various groups, each having p, q, r
items = n!
p! q! r!
Permutation of objects not all distinct: The number of mutually distinguishable
permutations of 'n' things, taken all at a time, of which p are alike of one kind, q
are alike of second such that p + q = n is n!
p!q!
If n outcomes can be repeated on r different things, total no. of permutations = r
n
Circular permutation of n things = (n - 1)!.
A deck of cards has 52 cards. There are four suits and each suit has 13 cards.
The total number of possible outcomes from a single throw of a perfect dice is 6.
The possible outcomes, of a single toss, of a fair coin are 2-H, T.
Permutation of n things taken r at a time, in which one particular thing always
occurs, is n1
r1r P .
Circular permutation of n things, if there is no difference between the clockwise
and anti-clockwise arrangement, is (n 1)!
2
n n n 1
r 1 r rC C C .
n r n n k
r k k r kC C C C .
n n n n n
0 1 2 nC C C .... C 2 .
n n n n n
0 1 2 nC C C .... C 2 .
n n n n n n n 1
0 2 4 1 3 5C C C .... C C C .... 2 .
Division of items into groups of unequal sizes: Number of ways in which (m + n)
items can be divided into two unequal groups containing 'm' and 'n' items is (m n)!
m!n!
.
Note: The number of ways in which (m + n) items are divided into two groups
containing 'm' and 'n' items is same as the number of combinations of (m + n)
things. Thus the required number mn
m
(m n)!
C
m!n!
.
Note : The number of ways of dividing (m + n + p) items among 3 groups of size
m, n and p respectively is = (Number of ways to divide) (m n p)!
m!n!p!
Note: The number of ways in which (mn) different items can be divided equally
into m groups each containing n objects and the order of group is important is mm
(mn)! 1 (mn)
m! .
(n!) m! (n!)
40 Ekoching
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items = n!
p! q! r!
Permutation of objects not all distinct: The number of mutually distinguishable
permutations of 'n' things, taken all at a time, of which p are alike of one kind, q
are alike of second such that p + q = n is n!
p!q!
If n outcomes can be repeated on r different things, total no. of permutations = r
n
Circular permutation of n things = (n - 1)!.
A deck of cards has 52 cards. There are four suits and each suit has 13 cards.
The total number of possible outcomes from a single throw of a perfect dice is 6.
The possible outcomes, of a single toss, of a fair coin are 2-H, T.
Permutation of n things taken r at a time, in which one particular thing always
occurs, is n1
r1r P .
Circular permutation of n things, if there is no difference between the clockwise
and anti-clockwise arrangement, is (n 1)!
2
n n n 1
r 1 r rC C C .
n r n n k
r k k r kC C C C .
n n n n n
0 1 2 nC C C .... C 2 .
n n n n n
0 1 2 nC C C .... C 2 .
n n n n n n n 1
0 2 4 1 3 5C C C .... C C C .... 2 .
Division of items into groups of unequal sizes: Number of ways in which (m + n)
items can be divided into two unequal groups containing 'm' and 'n' items is (m n)!
m!n!
.
Note: The number of ways in which (m + n) items are divided into two groups
containing 'm' and 'n' items is same as the number of combinations of (m + n)
things. Thus the required number mn
m
(m n)!
C
m!n!
.
Note : The number of ways of dividing (m + n + p) items among 3 groups of size
m, n and p respectively is = (Number of ways to divide) (m n p)!
m!n!p!
Note: The number of ways in which (mn) different items can be divided equally
into m groups each containing n objects and the order of group is important is mm
(mn)! 1 (mn)
m! .
(n!) m! (n!)
40 Ekoching
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Note: The number of ways in which (mn) different items can be divided equally
into m groups each containing n objects and the order of groups is not important
is m
(mn)! 1m
(n!) !
The number of non-negative solutions to the equation, 1 2 rx x .... x n is 1 2 rx x .... x n
The number of positive solutions to the equation, n1
1 2 r r 1x x .... x n is C .
15. Probability
(i) Probability = Favorable Cases
Total Cases
(ii) 0 Probability 1
(iii) P(A B) P(A) P(B) P(A B)
(iv) If events A and B are mutually exclusive, then P(A B) P(A) P(B)
(v) Probability of an event A not happening P(A ) 1 P(A)
(vi) If A and B are Independent Events, then P(A B) P(A) P(B)
(vii) In case of experiments with only 2 outcomes possible (tossing a coin,
passing or failing, hitting or not hitting a target etc.), the probability of
getting r successes in n trials n r n r
r(n r) is C p q
, where p is the
probability of success and q is the probability of failure.
(viii) P (A U B U C) = P(A) + P(B) + P(C) - P(A B) - P(B C) - P(A C) + P(A
B C).
(ix) P(A B) = P(A) x P(B), if A and B are independent events.
(x) P(A B) = 0, if A and B are mutually exclusive events.
Mutually Exclusive Events: Let S be the sample space associated with a random
experiment and let A, and A₂ be two events. Then A, and A2 are mutually exclusive
if 12AA .
Note – 1 : If A and B are two events associated with a random experiment,
then P(A U B) = P(A) + P(B) - P(A B)
Note-2: If A and B are mutually exclusive events, then P(A B) = 0,
therefore P(A B) = P(A) + P(B).
Note-3: If A, B, C are three events associated with a random experiment,
then P(A B C) = P(A) + P(B) + P(C) - P(A B)-P(B C)- P(A
C) + P(A B C).
Note-4: If A & B are two events associated with a random experiment, then
(i) P(A B) P(B) P(A B) (ii) P(A B) P(A) P(A B)
Let A and B be two events associated with a random experiment. Then the
probability of occurrence of A under the condition that B has already occurred and
P(B) = 0 is called conditional probability and it is denoted by A
P.
B
41 Ekoching
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into m groups each containing n objects and the order of groups is not important
is m
(mn)! 1m
(n!) !
The number of non-negative solutions to the equation, 1 2 rx x .... x n is 1 2 rx x .... x n
The number of positive solutions to the equation, n1
1 2 r r 1x x .... x n is C .
15. Probability
(i) Probability = Favorable Cases
Total Cases
(ii) 0 Probability 1
(iii) P(A B) P(A) P(B) P(A B)
(iv) If events A and B are mutually exclusive, then P(A B) P(A) P(B)
(v) Probability of an event A not happening P(A ) 1 P(A)
(vi) If A and B are Independent Events, then P(A B) P(A) P(B)
(vii) In case of experiments with only 2 outcomes possible (tossing a coin,
passing or failing, hitting or not hitting a target etc.), the probability of
getting r successes in n trials n r n r
r(n r) is C p q
, where p is the
probability of success and q is the probability of failure.
(viii) P (A U B U C) = P(A) + P(B) + P(C) - P(A B) - P(B C) - P(A C) + P(A
B C).
(ix) P(A B) = P(A) x P(B), if A and B are independent events.
(x) P(A B) = 0, if A and B are mutually exclusive events.
Mutually Exclusive Events: Let S be the sample space associated with a random
experiment and let A, and A₂ be two events. Then A, and A2 are mutually exclusive
if 12AA .
Note – 1 : If A and B are two events associated with a random experiment,
then P(A U B) = P(A) + P(B) - P(A B)
Note-2: If A and B are mutually exclusive events, then P(A B) = 0,
therefore P(A B) = P(A) + P(B).
Note-3: If A, B, C are three events associated with a random experiment,
then P(A B C) = P(A) + P(B) + P(C) - P(A B)-P(B C)- P(A
C) + P(A B C).
Note-4: If A & B are two events associated with a random experiment, then
(i) P(A B) P(B) P(A B) (ii) P(A B) P(A) P(A B)
Let A and B be two events associated with a random experiment. Then the
probability of occurrence of A under the condition that B has already occurred and
P(B) = 0 is called conditional probability and it is denoted by A
P.
B
41 Ekoching
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Thus A
P
B
Probability of occurrence of A under the condition that B has
already occurred. B
P
A
= Probability of occurrence of B under the condition that A has already
occurred.
Note-1: If A & B are two events associated with a random experiment, then B
P(A b) P(A).P
A
if A
P(A) 0 or P(A B) P(B).P if P(B) 0
B
Note 2: If A1, A2, A3 ------ An are n events related to a random experiment,
then
2
1 2 3 n 1
1 1 2
A A3
P(A A A _ _ _A ) P(A ).P .P _ _ _
A A A
n
2 n 1
A
P
A1 A _ _ A
Total Probability: Let S be the sample space and let E₁, E2.____En, be n mutually
exclusive and exhaustive events associated with a random experiment. If A is any
event which occurs with E1, or _ _ _ _ _ E₂ or En, then P(A) = P(E1). 1 2 n
1 2 n
A A A
P(A) P(E ).P P(E ).P ....... P(E ) / P .
E E E
Baye’s Rule : Rule: Let S be the sample space and let E₁, E2E, ben mutually exclusive
and exhaustive events associated with a random experiment. If A is any event
which occurs with E, or E2, _ _ _ _ _ or En, then 2 i i
n
ii
i1
E P(E ).P(A / E )
P
A
P(E ).P(A / E )
1. C
P(A) P(A ) 1.
2. C C C
P(A B ) P[(A B) ] 1 P(A B).
3. C C C
P(A B ) P[(A B) ] 1 P(A B).
4. If probability of an event in defined as the odds against or odds in favour
then the logic to solve this is as follows. If the odd in favour of happening of
an event are given to be in the ratio of p: q. Then the probability then the
event will happen is P
pq .
5. If the odds against happening of an event is given to be in the ratio of rs,
then the probability that the event will happen is s
rs . Hence it is to be
understood clearly what is being given in the question.
42 Ekoching
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P
B
Probability of occurrence of A under the condition that B has
already occurred. B
P
A
= Probability of occurrence of B under the condition that A has already
occurred.
Note-1: If A & B are two events associated with a random experiment, then B
P(A b) P(A).P
A
if A
P(A) 0 or P(A B) P(B).P if P(B) 0
B
Note 2: If A1, A2, A3 ------ An are n events related to a random experiment,
then
2
1 2 3 n 1
1 1 2
A A3
P(A A A _ _ _A ) P(A ).P .P _ _ _
A A A
n
2 n 1
A
P
A1 A _ _ A
Total Probability: Let S be the sample space and let E₁, E2.____En, be n mutually
exclusive and exhaustive events associated with a random experiment. If A is any
event which occurs with E1, or _ _ _ _ _ E₂ or En, then P(A) = P(E1). 1 2 n
1 2 n
A A A
P(A) P(E ).P P(E ).P ....... P(E ) / P .
E E E
Baye’s Rule : Rule: Let S be the sample space and let E₁, E2E, ben mutually exclusive
and exhaustive events associated with a random experiment. If A is any event
which occurs with E, or E2, _ _ _ _ _ or En, then 2 i i
n
ii
i1
E P(E ).P(A / E )
P
A
P(E ).P(A / E )
1. C
P(A) P(A ) 1.
2. C C C
P(A B ) P[(A B) ] 1 P(A B).
3. C C C
P(A B ) P[(A B) ] 1 P(A B).
4. If probability of an event in defined as the odds against or odds in favour
then the logic to solve this is as follows. If the odd in favour of happening of
an event are given to be in the ratio of p: q. Then the probability then the
event will happen is P
pq .
5. If the odds against happening of an event is given to be in the ratio of rs,
then the probability that the event will happen is s
rs . Hence it is to be
understood clearly what is being given in the question.
42 Ekoching
Your door to future
16. Clocks & Calendars
A. Clocks
A clock is a complete circle having 360 degrees. It is divided into 12 equal parts i.e.
each part is 360/12 = 30°. As the minute hand takes a complete round in one hour
it covers 360° in 60 min. In 1 min. it covers 360/60 = 6°/ minute. Also, as the hour
hand covers just one part out of the given 12 parts in one hour, this implies it
covers 30° in 60 min. i.e. ½ per minute. This implies that the relative speed of the
minute hand is 6-%½= 5% degrees.
Every hour, both the hands coincide once. In 12 hours, they will coincide 11 times.
It happens due to only one such incident between 12 and 1'o clock.
The hands are in the same straight line when they are coincident or opposite to
each other.
When the two hands are at a right angle, they are 15-minute spaces apart. In one
hour, they will form two right angles and in 12 hours there are only 22 right angles.
It happens due to right angles formed by the minute and hour hand at 3'o clock
and 9'o clock.
When the hands are in opposite directions, they are 30-minute spaces apart
If a clock indicates 8.15, when the correct time is 8, it is said to be 15 minutes too
fast. On the other hand, if it indicates 7.45, when the correct time is 8, it is said to
be 15 minutes too slow.
NOTE: If both the hour hand and minute hand move at their normal speeds, then
both the hands meet after 5
65
11 minutes.
You have a formula to compute the angle between the two hands of a clock in any
time.
Formula :- angle = (30H) (5.5M) , where H represents hour hand and M
represents minute hand.
B. Calendars
In an ordinary year there are 365 days, which means 52 7 1 , or 52 weeks and
one day. This additional day, is called an odd day. Further, every 100 year starting
from 1st AD, is a non-leap year, but every 4th century year is a leap year. So any
year divisible by 400 will be a leap year e.g.: 1200, 1600 and 2000. And the years
1800, 1900 will be non leap years as they are divisible by 100, but not 400.
The concept of odd days is very important in calendars. In a century - i.e. 100 years,
there will be 24 leap years and 76 non-leap years. This means that there will be 24 2 76 1 124
odd days. Since, 7 odd days make a week, to find out the net
odd days, divide 124 by 7. The remainder is 5. This is the number of odd days in a
century. You may memorise the following points related to the concepts of
calendars to save time during the paper.
100 years give us 5 odd days as calculated above.
200 years give us 5 2 = 10-7 (one week) - 3 odd days.
300 years give us 5 3=15-14 (two weeks) - 1 odd day.
400 years give us {5 4+1 (leap century)} -21) - 0 odd days.
Month of January gives us 31-28 = 3 odd days.
Month of February gives us 28-28 = 0 odd day in a normal year and 1 odd day in
a leap year and so on for all the other months. 43 Ekoching
Your door to future
A. Clocks
A clock is a complete circle having 360 degrees. It is divided into 12 equal parts i.e.
each part is 360/12 = 30°. As the minute hand takes a complete round in one hour
it covers 360° in 60 min. In 1 min. it covers 360/60 = 6°/ minute. Also, as the hour
hand covers just one part out of the given 12 parts in one hour, this implies it
covers 30° in 60 min. i.e. ½ per minute. This implies that the relative speed of the
minute hand is 6-%½= 5% degrees.
Every hour, both the hands coincide once. In 12 hours, they will coincide 11 times.
It happens due to only one such incident between 12 and 1'o clock.
The hands are in the same straight line when they are coincident or opposite to
each other.
When the two hands are at a right angle, they are 15-minute spaces apart. In one
hour, they will form two right angles and in 12 hours there are only 22 right angles.
It happens due to right angles formed by the minute and hour hand at 3'o clock
and 9'o clock.
When the hands are in opposite directions, they are 30-minute spaces apart
If a clock indicates 8.15, when the correct time is 8, it is said to be 15 minutes too
fast. On the other hand, if it indicates 7.45, when the correct time is 8, it is said to
be 15 minutes too slow.
NOTE: If both the hour hand and minute hand move at their normal speeds, then
both the hands meet after 5
65
11 minutes.
You have a formula to compute the angle between the two hands of a clock in any
time.
Formula :- angle = (30H) (5.5M) , where H represents hour hand and M
represents minute hand.
B. Calendars
In an ordinary year there are 365 days, which means 52 7 1 , or 52 weeks and
one day. This additional day, is called an odd day. Further, every 100 year starting
from 1st AD, is a non-leap year, but every 4th century year is a leap year. So any
year divisible by 400 will be a leap year e.g.: 1200, 1600 and 2000. And the years
1800, 1900 will be non leap years as they are divisible by 100, but not 400.
The concept of odd days is very important in calendars. In a century - i.e. 100 years,
there will be 24 leap years and 76 non-leap years. This means that there will be 24 2 76 1 124
odd days. Since, 7 odd days make a week, to find out the net
odd days, divide 124 by 7. The remainder is 5. This is the number of odd days in a
century. You may memorise the following points related to the concepts of
calendars to save time during the paper.
100 years give us 5 odd days as calculated above.
200 years give us 5 2 = 10-7 (one week) - 3 odd days.
300 years give us 5 3=15-14 (two weeks) - 1 odd day.
400 years give us {5 4+1 (leap century)} -21) - 0 odd days.
Month of January gives us 31-28 = 3 odd days.
Month of February gives us 28-28 = 0 odd day in a normal year and 1 odd day in
a leap year and so on for all the other months. 43 Ekoching
Your door to future
In total first six months i.e. January to June give us 6 odd days in a normal year and
7-7 = 0 odd days in a leap year. This is going to help, when you want to find a day,
which is after 30th June.
In total first nine months i.e. January to September give us 0 odd day in a normal
year and 1 odd day in a leap year.
Now, if we start from 1st January 0001 AD; for 0 odd day, the day will be Sunday;
for 1 odd day, the day will be Monday; for 2 odd days, it will be Tuesday; for 3 odd
days, it will be Wednesday and so on.
There are two types of questions, one in which a reference day is given and in the
other variety, no reference day is given.
17. Mean and Basic Statistics
Arithmetic mean of the numbers a and b = a + b/2
Geometric mean of the numbers a and b = ab , if a > 0 and b> 0
Comparing an arithmetic mean and a geometric mean: a + b/2≥ Vab, if a > 0 and
B > 0 If a given number is split into two parts, then the product of the two parts
will be the highest when they are equal.
If a given number is split into two positive multiplicative parts, then the sum of the
two parts will be the least when the two parts are the square roots of the number.
Arithmetic mean - The A.M of X1, X2,...,X, is 1 2 nx x ....... X
n
Geometrix men – The G.M. of 1 2 nx ,x ....x is n
1 2 nx x ..... x
Harmonic Mean – The H.M of 1 2 nx ,x ........,x is 1 2 n
n
1 1 1
.....
x x x
Median - To calculate the median of a given set of numbers, arrange the
frequencies in the ascending order, if the number of elements is odd, the median
is (n+1)/2th term and if even then the average of the two middle terms is the
median of the whole group.
Mode - The value occurring with the maximum frequency is called the mode.
A.M G.M H. M, and all of them are equal if all the values of x, are equal.
If X1, X2.....Xn are points in the data, and if x is the mean, then Variance
= 2
(xi x)
n
Standard Deviation = Variance
44 Ekoching
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7-7 = 0 odd days in a leap year. This is going to help, when you want to find a day,
which is after 30th June.
In total first nine months i.e. January to September give us 0 odd day in a normal
year and 1 odd day in a leap year.
Now, if we start from 1st January 0001 AD; for 0 odd day, the day will be Sunday;
for 1 odd day, the day will be Monday; for 2 odd days, it will be Tuesday; for 3 odd
days, it will be Wednesday and so on.
There are two types of questions, one in which a reference day is given and in the
other variety, no reference day is given.
17. Mean and Basic Statistics
Arithmetic mean of the numbers a and b = a + b/2
Geometric mean of the numbers a and b = ab , if a > 0 and b> 0
Comparing an arithmetic mean and a geometric mean: a + b/2≥ Vab, if a > 0 and
B > 0 If a given number is split into two parts, then the product of the two parts
will be the highest when they are equal.
If a given number is split into two positive multiplicative parts, then the sum of the
two parts will be the least when the two parts are the square roots of the number.
Arithmetic mean - The A.M of X1, X2,...,X, is 1 2 nx x ....... X
n
Geometrix men – The G.M. of 1 2 nx ,x ....x is n
1 2 nx x ..... x
Harmonic Mean – The H.M of 1 2 nx ,x ........,x is 1 2 n
n
1 1 1
.....
x x x
Median - To calculate the median of a given set of numbers, arrange the
frequencies in the ascending order, if the number of elements is odd, the median
is (n+1)/2th term and if even then the average of the two middle terms is the
median of the whole group.
Mode - The value occurring with the maximum frequency is called the mode.
A.M G.M H. M, and all of them are equal if all the values of x, are equal.
If X1, X2.....Xn are points in the data, and if x is the mean, then Variance
= 2
(xi x)
n
Standard Deviation = Variance
44 Ekoching
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18. Trigonometry
(i) Measurement of Angle : Mainly there are three systems for measuring
angles.
Sexagesimal system: In this system, angle is measured in degrees.
I right angle 90 ,1 60' and 1' 60 .
Centesimal system : In this system angles is measured in grades.
I right angle = gg
100 ,1 100' and 1’ = n
100
Cricular Measure : In this system, angle is measured in radius.
The angle subtended at the centre of a circle by an arc of length equal to its
radius is 1 radian, written as 1 . 0R
180 200 2 right angles
(ii) Trigonometric Ratios:
Perp. PM Base AM
sin ;cos ;
Hyp. AP Hyp. AP
Perp. PM
tanθ;
Base AM
1 1 cos θ
cosesθ= ;secθ= ;cosθ= .
sinθ cosθ sinθ
(iii) Identities:
(i) sin
tan
cos
(ii) cos
cos
sin
(iii) 22
sin cos 1 (iv) 22
1 tan sec
(v) 22
1 cot cosec
(iv) Values of T – Ratios:
Angle sin cos tan 0
0 1 0 30
6
1
2 3
2 1
3 45
4
1
2 1
2 1 60
3
3
2 1
2 3 90
2
1 0 180
0 -1 0
(v) sign of T – ratios;
1
st
Quadrant: All Positive.
2
nd
Quadrant : sin & cosec positive. 45 Ekoching
Your door to future
(i) Measurement of Angle : Mainly there are three systems for measuring
angles.
Sexagesimal system: In this system, angle is measured in degrees.
I right angle 90 ,1 60' and 1' 60 .
Centesimal system : In this system angles is measured in grades.
I right angle = gg
100 ,1 100' and 1’ = n
100
Cricular Measure : In this system, angle is measured in radius.
The angle subtended at the centre of a circle by an arc of length equal to its
radius is 1 radian, written as 1 . 0R
180 200 2 right angles
(ii) Trigonometric Ratios:
Perp. PM Base AM
sin ;cos ;
Hyp. AP Hyp. AP
Perp. PM
tanθ;
Base AM
1 1 cos θ
cosesθ= ;secθ= ;cosθ= .
sinθ cosθ sinθ
(iii) Identities:
(i) sin
tan
cos
(ii) cos
cos
sin
(iii) 22
sin cos 1 (iv) 22
1 tan sec
(v) 22
1 cot cosec
(iv) Values of T – Ratios:
Angle sin cos tan 0
0 1 0 30
6
1
2 3
2 1
3 45
4
1
2 1
2 1 60
3
3
2 1
2 3 90
2
1 0 180
0 -1 0
(v) sign of T – ratios;
1
st
Quadrant: All Positive.
2
nd
Quadrant : sin & cosec positive. 45 Ekoching
Your door to future
3
rd
Quadrant : tan & cot positive.
4
th
Quadrant : cos & sec positive.
Remember: I II III IV
All sin tan cos
(vi) Range of T – Ratios:
(i) -1 sin 1 and - 1 ≤ cos 0 ≤ 1
Thus, sinθ1 andcosθ1
The value of sin θ is never greater than 1 and never less than -1.
The value of cos is never greater than 1 and never less than -1.
(ii) cosec θ ≥ 1 and cosec θ -1.
(iii) sec θ ≥ 1 and sec θ -1.
(iv) tan θ may assume any value.
(vii) Increasing & Decreasing Functions:
(i) The value of sin increase from to
22
. As increases in this
interval, then sin also increases.
(ii) 1
st
Quadrant: sin increases from 0 to 1; cos decreases from 1 to 0
and tan increases from 0 to .
(iii) 2
nd
Quadrant: sine decreases from 1 to 0; cos decreases from 0 to
-1; tan decreases from to 0.
(iv) 3
rd
Quadrant: sin 0 decreases from 0 to -1; cos e increases from 1 to
0; tan increases from 0 to .
(v) 4
th
Quadrant: sin increases from -1 to 0; cos increases from 0 to 1;
tan decreases from ∞ to 0.
(viii) T – Ratios of Negative, Complementary, Supplementary Angles etc.
(i) sin (-θ ) = -sin θ , cos (-θ ) = cos θ , tan (-θ ) = -tan θ .
(ii) sin (90θ) cos θ; cos(90 - θ)=sinθ;tan(90 θ) cotθ.
(iii) sin(90θ) cos θ; cos(90 θ)=-sinθ;tan(90 θ) cotθ.
(iv) sin(180θ) sin θ; cos(180 θ)=-cosθ;tan(180 θ)tanθ.
(v) sin(180θ) sin θ; cos(180 θ)=-cosθ;tan(180 θ)tanθ.
(vi) sin(360θ) sin θ; cos(360 θ)=cosθ;tan(360 θ) tanθ.
(vii) sin(360θ) sin θ; cos(360 θ)=cosθ;tan(360 θ) tanθ.
(ix) Sum & Difference Formula:
(i) sin(x y) sin x cosy cosxsiny.
(ii) sin (x – y) = sin x cos y – cos x sin y.
(iii) cos (x + y) = cos x cosy – sin x sin y
(iv) cos(x y) cosxcosy sinxsiny.
(v) 2sinxcosy sin(x y) sin(x y).
(vi) 2cosxsiny sin(x y) sin(x y).
(vii) 2 cos x cos y = cos (x + y) + cos (x – y).
(viii) 2 sin x sin y = cos (x – y) – cos (x + y).
(ix) sin
2
x – sin
2
y = sin (x + y). sin (x – y ).
(x) 22
cos x sin y cos(x y).cos(x y). 46 Ekoching
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rd
Quadrant : tan & cot positive.
4
th
Quadrant : cos & sec positive.
Remember: I II III IV
All sin tan cos
(vi) Range of T – Ratios:
(i) -1 sin 1 and - 1 ≤ cos 0 ≤ 1
Thus, sinθ1 andcosθ1
The value of sin θ is never greater than 1 and never less than -1.
The value of cos is never greater than 1 and never less than -1.
(ii) cosec θ ≥ 1 and cosec θ -1.
(iii) sec θ ≥ 1 and sec θ -1.
(iv) tan θ may assume any value.
(vii) Increasing & Decreasing Functions:
(i) The value of sin increase from to
22
. As increases in this
interval, then sin also increases.
(ii) 1
st
Quadrant: sin increases from 0 to 1; cos decreases from 1 to 0
and tan increases from 0 to .
(iii) 2
nd
Quadrant: sine decreases from 1 to 0; cos decreases from 0 to
-1; tan decreases from to 0.
(iv) 3
rd
Quadrant: sin 0 decreases from 0 to -1; cos e increases from 1 to
0; tan increases from 0 to .
(v) 4
th
Quadrant: sin increases from -1 to 0; cos increases from 0 to 1;
tan decreases from ∞ to 0.
(viii) T – Ratios of Negative, Complementary, Supplementary Angles etc.
(i) sin (-θ ) = -sin θ , cos (-θ ) = cos θ , tan (-θ ) = -tan θ .
(ii) sin (90θ) cos θ; cos(90 - θ)=sinθ;tan(90 θ) cotθ.
(iii) sin(90θ) cos θ; cos(90 θ)=-sinθ;tan(90 θ) cotθ.
(iv) sin(180θ) sin θ; cos(180 θ)=-cosθ;tan(180 θ)tanθ.
(v) sin(180θ) sin θ; cos(180 θ)=-cosθ;tan(180 θ)tanθ.
(vi) sin(360θ) sin θ; cos(360 θ)=cosθ;tan(360 θ) tanθ.
(vii) sin(360θ) sin θ; cos(360 θ)=cosθ;tan(360 θ) tanθ.
(ix) Sum & Difference Formula:
(i) sin(x y) sin x cosy cosxsiny.
(ii) sin (x – y) = sin x cos y – cos x sin y.
(iii) cos (x + y) = cos x cosy – sin x sin y
(iv) cos(x y) cosxcosy sinxsiny.
(v) 2sinxcosy sin(x y) sin(x y).
(vi) 2cosxsiny sin(x y) sin(x y).
(vii) 2 cos x cos y = cos (x + y) + cos (x – y).
(viii) 2 sin x sin y = cos (x – y) – cos (x + y).
(ix) sin
2
x – sin
2
y = sin (x + y). sin (x – y ).
(x) 22
cos x sin y cos(x y).cos(x y). 46 Ekoching
Your door to future
(x) Some More Formulae:
(i) C D C D
sin C sinD 2sin cos
22
(ii) C D C D
sin C sinD 2cos sin
22
(iii) C D C D
cos C cosD 2cos cos
22
(iv) C D C D
cos C cosD 2sin sin
22
(xi) Tangent Formulae:
(i) tan x tan y
tan(x y)
1 tan x tan y
(ii) tan x tan y
tan (x y)
1 tan x tan y
(xii) T – Ratios of Multiple Angles:
(i) sin 2x = 2 sin x cos x
(ii) cos 2x = cos
2
x – sin
2
x = 2cos
2
x – 1 = 1 – 2 sin
2
x.
(iii) 1 + cos 2x = 2 cos
2
x and 1 – cos 2x = 2 sin
2
x.
(iv) sin 3x = 3 3 sin x – 4 sin
3
x
(v) cos 3x = 4 cos
3
x – 3 cos x
(vi) 2
2tanx
tan2x
1 tan x
(vii) 3
2
3tanx tan x
tan3x
1 3tan x
(viii) 2
2
1 tan x
cos2x
1 tan x
(ix) 2
20tanx
sin2x
1 tan x
(xiii) T – Ratios of Sub – multiple Angles:
(i) sin x = 2 sin (x / 2) cos (x/ 2)
(ii) cos x = cos
2
2 2 2x x x x
sin 2cos 1 1 2sin
2 2 2 2
(iii) 2
2tan(x / 2)
tan x
1 tan (x / 2)
(iv) 1 – cos x = 2 sin
2
x
2 and 1 + cos x = 2 cos
2
x
2
(v) 2
2tan (x / 2)
sin x
1 tan (x / 2)
(vi) 2
2
1 tan (x / 2)
cosx
1 tan (x / 2)
47 Ekoching
Your door to future
(i) C D C D
sin C sinD 2sin cos
22
(ii) C D C D
sin C sinD 2cos sin
22
(iii) C D C D
cos C cosD 2cos cos
22
(iv) C D C D
cos C cosD 2sin sin
22
(xi) Tangent Formulae:
(i) tan x tan y
tan(x y)
1 tan x tan y
(ii) tan x tan y
tan (x y)
1 tan x tan y
(xii) T – Ratios of Multiple Angles:
(i) sin 2x = 2 sin x cos x
(ii) cos 2x = cos
2
x – sin
2
x = 2cos
2
x – 1 = 1 – 2 sin
2
x.
(iii) 1 + cos 2x = 2 cos
2
x and 1 – cos 2x = 2 sin
2
x.
(iv) sin 3x = 3 3 sin x – 4 sin
3
x
(v) cos 3x = 4 cos
3
x – 3 cos x
(vi) 2
2tanx
tan2x
1 tan x
(vii) 3
2
3tanx tan x
tan3x
1 3tan x
(viii) 2
2
1 tan x
cos2x
1 tan x
(ix) 2
20tanx
sin2x
1 tan x
(xiii) T – Ratios of Sub – multiple Angles:
(i) sin x = 2 sin (x / 2) cos (x/ 2)
(ii) cos x = cos
2
2 2 2x x x x
sin 2cos 1 1 2sin
2 2 2 2
(iii) 2
2tan(x / 2)
tan x
1 tan (x / 2)
(iv) 1 – cos x = 2 sin
2
x
2 and 1 + cos x = 2 cos
2
x
2
(v) 2
2tan (x / 2)
sin x
1 tan (x / 2)
(vi) 2
2
1 tan (x / 2)
cosx
1 tan (x / 2)
47 Ekoching
Your door to future
(xiv) T – Ratios of Some Special Angles:
(i) sin 31
15 cos75
22
(ii) cos 31
15 sin75
22
(iii) 51
18 cos72
4
(iv) cos 10 2 5
18 sin72
4
(v) sin 10 2 5
36 cos54
4
(vi) 51
36 sin54
4
(vii) 1 2 2
sin22
22
(viii) 1 2 2
cos 22
22
48 Ekoching
Your door to future
(i) sin 31
15 cos75
22
(ii) cos 31
15 sin75
22
(iii) 51
18 cos72
4
(iv) cos 10 2 5
18 sin72
4
(v) sin 10 2 5
36 cos54
4
(vi) 51
36 sin54
4
(vii) 1 2 2
sin22
22
(viii) 1 2 2
cos 22
22
48 Ekoching
Your door to future
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